I personally don't enjoy playing my rogue as much as I did in WotLK but it could still be fun. The new talent system in MoP really homogenized our specs so they don't feel quite as different as they used to.
We're still quite good in PvP. Still close top tier/gladiator range, though slightly harder than earlier seasons in my opinion. All depends on your comp. We can definitely be scary in 1v1s though.
I haven't had much trouble solo'ing either, in good gear. I still prefer using my priest, but I've solo'd half the bosses in Ulduar 10 on my rogue, only stopping because I got bored. Lol. as for changing specs, subtlety is basically the cookie-cutter spec for PvP and while I hear it's a viable option for PvE again, I'm sure it's annoying to perform well with, so I still stick to having a different spec for PvE.
All I can really say is try it out for yourself and see what you like.
Coming from someone who's played a Rogue in every expansion at some point: From a class mechanic and play-style point of view they're pretty fun - in actual play (I'm not talking numbers) I'd say they're "meh" at best now.
They are very reliant on gear (specifically weapons) meaning they're bleh in both PvE and PvP until geared and extremely squishy when levelling - global or reset usually.
Energy regen is god awful and making Sinister Strike cost 50 Energy was just retarded for anything outside of a Raid geared Rogue under AR or Hero.
Personally I don't like the fact ~60% of your damage is passive in raids, more as Assassination but still stupid-high as Combat.
With that said, even though I main a Frost DK for PvE (Only class which is melee with the 1sec GCD and no waiting time because I hate waiting around), Rogue will always be my class of choice for... uhh... anything. Especially just messing around on.
So to give relative answers:
PvP - Fun when fully geared, fucking awful otherwise.
Solo Content - Wouldn't know tbh.
PvE - Always pretty high on the charts with at least one spec. Decent cleave as Combat or AoE as Assass. Amazing mobility with BoS/ShS & Sprint. Stupid amounts of survival in PvE with a mix of Feint/CloS/Cheat Death/Evasion.