Ok so I will go ahead and be the positive WoW shill that I am and give you my run down.
First this expansion uses the foundation systems of Legion which is GOOD. Obviously it was well received regardless of what the "sky is falling" crowd will tell you. Legion to me was basically WoW 2.0 in that it introduced new systems that can carry the game forward in different variations.
Azerite Power AKA Artifact Power [AP] - Bringing this system back was the right move. It creates a grind and replay-ability of all the systems in BFA. I find it nice that it doesn't have to go into a certain spec and it's character wide. Makes for a more alt friendly change but keeps the grind. The Heart of Azeroth pendant is the backbone of our AP leveling which then trickles into..
Azerite Armor - These pieces of armor are introduced in the initial questline of BFA, into questing, through dungeons, into raids and PvP. You level of up your Pendant to then apply it into your Helm/Shoulders/Chest. This can not titanforge which is a nice touch. So far the Mythic traits are pretty GOOD not 2/4 piece set good. I expect we get these in the first "raid tier" of the expansion. Which should be Azshara in 8.1 if that is in fact her raid. Overall I think it's Blizzard experimenting here. I have found amazing traits at Mythic dungeon levels for my Prot Paladin. You will obviously be farming multiples of the SAME armor which creates different SETS for different situations. NOW IS THIS IDEAL? I kinda don't like it but we been doing already in previous expansions. I.E. - ST set/AoE Set/Balance etc. NO secondary stats....that I don't like. Prot Paladin at 8% haste at iLvL 357?
WEAPON DROPS ARE BACK and can only Warforge
World Quests - They are back and rightfully so they tie into our grind/rep grind and start off. Cool things to note WQ now have weapons and good trinkets. Not just stat sticks but ones that increase primary stats and some that have dmg procs. They drop War Resources/Gold/AP/Armor and Weapons.
Reputation - Pretty cool yeah I mean rep grind. Least now we get relevant gear to start new raids
Factions Hubs - Thank f00king TIRION. If you have never sat in Boralus at night then you just have to. The Hubs are HUGE and filled with fun, secrets, quests and more. Horde city is just a tower of beauty and come on now after being snubbed on Karabor how are you not happy for this.
War Campaign - Also located in your major city in BFA houses the replacement for the Class Order hall. Now i loved my order and Blizzard is tuning this down in BFA. As you level your faction commander gives you quests to venture into the opposite factions land. There is a Mission Table but its VERY LIGHT like 4-5 followers. Also an upgrade station which affects your Warfronts and out door adventures. This could be your first taste of Warmode PvP but be careful as of right now outside of the quest hub you invade mobs are 120.
Warmode - This is actually a bold and smart move by Blizzard. No more templates, Gear matters again, and it is on US. This is a player CHOICE to fight now. Your PvP servers are now basically PvE. Once you turn on Warmode then it's game. There is a bounty system where if you kill enough of opposite faction you have a bounty of your head and people will look for you. There are AIR DROPS (lol wtf) that just like in BR people will fight over that can contain gear and other loot. Conquest system is back and as you level you get gear. Strongboxes still exist but they are mixing the old way and new way of gearing. Also cool to note if you get enough conquest you get a PvP only chest every reset like PvE'ers do for Mythic. Once again Warmode is a PLAYER CHOICE and it is up to us to go out there fight. Pretty much Blizzard said eff it you want to go at it you can...no then PVE casual pleb.
(Note you get 10% experience from quests mobs for enabling this! At 120 you get 10% more from World Quests resources which Mythic Raiders will probably be all over)
Warfronts - Yeah I know NOT PvP but it brings back that WC3 RTS feel for you OG's out there. Battles are about 20-30 minutes long and thus far after every battle you get gear. This may change. But players think that is it. It's NOT. There is a War Effort that needs to go on. In your major city you will have profession/Gold/War Resource turn ins that give you a boat load of AP and help with your wekly effort to get back into battle. Once you've won you have access to what I call NEW ARATHI Highlands. Rares everywhere 4/5 mounts to farm from these, tons of toys, gear and much more. Plus the World Boss. More Warfront locations have been datamined so expect more old zones being converted for Warfront battles.
Island Expeditions - This one I WAS VERY HYPED for but then was like MEH. It is a huge source so they say of weekly Azerite. There are 6-9 different islands. 3v3 You against Blizzard made AI which is fun to go up against. You collect Azerite first to 4k/6k/9k wins. N/H/M difficulty. There is a PvP where you go up against 3 other players and this could eventually become competitive and might be next thing Blizzard tries to push like with MDI. It IS A DYNAMIC world. The same Island you went to might not be same if you get it again in queue. There are quests and fun little activities to do while in there.
NEW ZONES - Ok I serously laugh when people say that BFA is a reskinned Legion with new zones. Come on. Has anyone actually seen Drustvar? Voldun? Nazmir? This expansion gives me the MOP feel. New enemies, new faces, new stories. Kind of like when we first got to up against the Klaxxi, Mogu etc. Each zone has their unique story lines. Alliance is OK. The Azshara story in Stormsong valley is legit...Drustvar is creepy as f00k. Horde side has the real deal quests with Blood Trolls, Blood Gods, Rastakhan, Zul, the Sethrak (sp?). There is nothing LEGION about this. Screw Fel glad it's finally gone and we can move on.
No Suramar zone but datamined areas like Najatar, Blighted lands, Plunder Isle and possibly Old God lands could surface. (really dudes people cry about Suramar in legion then cry when BFA doesn't start with one?)
Mythic Plus - Probably the most loved feature. 10 Dungeons to start. ALL very unique. Boss mechanics are tough, every trash pack feels like it can destroy you. Tyrannical and Fortified now start at +2 which gives for more better feel to Legion difficulty jump in certain levels like going from 8 to a 10 in early Legion, or 15 to a 17. Temple of Sethrallis, Waycrest Manor, King's Rest are some of my favorites. Each tell a good story related to what we went through in the leveling zones.
Raids - Ion mentioned that BFA will follow pretty much the same patch cycle as Legion. (WoD 2.0 AMIRITE?) First raid Uldir is a good starting point. Titan experimental facility in which we take on the Blood God G'Hunn. (once again kick ass Horde Story) Mythic difficulty from testing has shown to have some pretty nice challenges to it. I expect there ot be 3-4 Raids with a Mini Raid. Think one was datamined after Uldir in Zandalar?
Allied Races - Say what you will but people love this stuff. Allied races with their own unique racials to leave you siming for days! Sorry DK's 4 so far and probably more to come. This is pretty much the "come back and try this one out" of the expansion.
Mounts/pets/Puzzles - TONS AND TONS of these. Puzzles I can't wait for, that community is insane.
Communities Feature - Like circles in Wildstar and Link Shells in FFXIV this is a GREAT way to build communities focued on different aspects of games. M+ communities, weekend raiders, casual players, achievement hunters, for me streamer community will be big. This is a very very underrated feature.
Pre-Patch content - Burning of Tree, Battle for Lorderon. Not weak but definitely not the Level your alt hype of Legion Pre-Patch.
Now for some things that are on the controversial side.:
No Tier sets - Obviously a product of Azerite Armor. We will see how this goes. I welcome the not having to keep higher iLvL gear in your bags for 2/4 piece sets
GCD changes - Adapt or go home? Yeah man it sucks. Especially having defensives there but they seem firm on their stance. Although they have made changes to some abilities here and there. I don't see this "FFXIV" slow down though. Very exaggerated.
Mythic Plus no armor changes allowed while in dungeon - Why? Do not agree
Personal Loot/Master Loot - Why? Do not agree.
CLASS CHANGES AND BALANCE - Oh man lol. I like fact that they kept some of the good traits and lego equip on our Azerite traits and talents and Passives. But seeing some classes and specs NOT get theirs was disappointing. Plenty of specs got new talents and new passives to play with. Some got snubbed and robbed. It happens.
Once again let's not confuse TUNING and CLASS CHANGES. Tuning has been going on for months now and class changes have been made. Some will change in future. Welcome to every expansion. Yes I know your spec is borked and you're mad. This happens EVERY TIME. Legion pruning sheit posts come to mind and it will happen for future expansions.
BUGS on BETA - yeah I mean come on you know their QA team is ahead of our versions let's not go crazy cause you fell through the world or crit error'd in Arathi
In end BFA has me HYPED not SUPER HYPED but HYPED enough that I will get the same fun and replay-ability I got in Legion. It is a new world with great systems continued and adjusted. Having the world revolve around AP grind is a good move and glad it is back.
I probably missed a lot but this is all I got. I'm spent. And yes I realize I play WoW for a living and the game prospering is good for me and other content creators. Hence I realize my opinion is already skewed to a lot you. But these are just thoughts going in.