GW2 is a must play for people who want to know what else an MMO can offer, because it makes many wonderful offers that are very different from any other MMO I've run into. It's the only time I remember thoroughly enjoying leveling in an MMO. All my friends who bought it and gave it a chance, were really happy with the leveling.
It's hard to say how it differs really. You just have to try it.
But .. be warned .. no DPS rotations, buttons/skills are very simplistic. The game offers challenge in reaction/movement skill not repeating a rotation. There is absolutely no end-game of any kind, there used to be a Living Story but that got scrapped mostly and still was only worth 1.5 hours of gameplay every two weeks.
End game dungeons are run for transmog, and are basically a rush/skip everything possible to get to the end kinda deal ASAP. Tuning is just god awful, anything that isn't a normal mob can nearly insta-kill you and most dungeon trash can easily annihilate a group. There is no aggro, the self healing you have cannot keep up with the damage if you find yourself the unfortunate target of the boss's attention.
You can hit up the Auction House and buy full end-game gear, and then when you look up what to do on Google, you'll find the answer is often: "Create a new character" or "finish exploring the world".
BUT they are adding raids in the future .. however .. 1: They can't tune a game to save their lives and 2: They stated there will be no gear increases, or power rewards for doing it. Purely a challenge thing, and challenge in this game is another word for frustrating.
Looking at the game through the "lens of Dev", I found many inspirations and impressive moves by them that were ultimately doomed by their inability to capitalize on them or provide a driving end-game.
I understand they didn't like the grind but .. the grind is what brings us back tomorrow. The promise of a bit more power, or more importantly .. self improvement. Of which this game offers zero at max level. If you have transmog gear you like, you're basically done, which is a really big shame. I'd still love to be playing it but I just couldn't find anything that was worth doing.
GW2 had a great leveling experience, the outdoor world boss/raids were amazing the first few times. What it needs, IMO, is more meaningful skill sets that feel more like they are capturing the class feel. The talents need to be alot more meaningful and interesting. They need to tune mobs to be fair, especially for a game with no tank and no healer to save you. And they need to find a compromise between their "no grind" stance and the lack an end-game.
GW2 is not WoW and does not need to be but it needs to be enjoyable, and needs a reason to come back every day. For all it's achievements otherwise, it just doesn't offer those aspects at the max level.
My opinion, of course. I honestly enjoyed leveling the 3-4 characters I played on there. So I don't mean to come off entirely negatively, I was impressed in the leveling and bosses. Just, I need an end-game to stay.
But of course, isn't GW2 free to play now? (I bought the box right at launch because I was really reeled in by their promises -- which I understand they made with the best of intentions even if they couldn't deliver on them). You got nothing to lose in giving it a try, man. I mean, well .. you ALWAYS have something to lose .. time .. if you don't mind losing that, go for it. Oh and it's about an hour per level, steady, all the way. Less you run headlong into a ton of events going on.