Depends what kind of player you are/what you're looking for.
Levelling is pretty good all in all and I think it's more fun in a party/with a partner, so you'd have that going for you (though unless you are the same race it might be a little troublesome meeting up early on). The one thing they really did right was making XP rewards meaningful from exploration/crafting. The zones are pretty, but ultimately kind of generic imo. The continent is realistically laid out (relatively) but as a result most of the zones don't really have a theme beyond "mountainous" or "grassy" or "snowy".
If you're looking for a story, it's ok at best. I think it'd be a lot better if the stories weren't essentially identical post the Claw Island (about level 40 iirc) event; even then prior to that they're roughly analogous it seems. It's made worse by (a lot of / very) poor writing and voice acting; but you still run into some genuinely cool characters.
If you're a 'raider' then I'd look elsewhere. The only thing to do when you hit 80 is complete exploration (pointless doing anything except the final maps unless you actually enjoy the exploring) and grind dungeons (think badge farming) for mats for a legendary item. I think the most fun and satisfying thing to do in an MMO is team up and play. Unfortunately GW2's [lack of] mechanics really kill that because every boss is the same except for the occasional gimmick.
If you PVP then it's probably worth checking out. It's very easy to create a character and hop right into the "heart of the mists" (pvp only zone) and start playing with no PvE influence [everyone is 80 and can choose from the same gear], which a lot of my friends have been really enjoying. Personally I'd stick with the tourneys (World pvp way overrated imo) but they're probably best enjoyed with friends or else you're stick with random players.
This is a pretty good subscription.
However the map zones are not as generic as Dark here mentions, as there is also desolate lava/volcano type mountains with dead forests and a few zones that were tooo full of water. And each map is unique. Sure it may be "another forest map" but honestly... there is only so many eco-zones that exist. Blame that on mother nature for not creating more exciting "realistic" types of nature.
I liked the voice acting, though agreeably the writing isn't top notch and the story is decent. Especially my story. I loved the lv 30 part a lot. So if looking for a game with a story (like Final fantasy or w/e) this isn't it. (However, its personal character story is more than I can say for WoW which was never a "story" based MMO. It has a LOT of lore via quests and whats going on around each zone, but no actual story at why your character is doing what it is they are doing.)
This def. is not a raiding MMO. However the raiding scene is starting to feel old to a lot of people it seems like. This is all personal taste though and as dark has pointed out if you love raiding stay on WoW. May love a game that doesnt require set schedules on set days with X amoutn of people, and may not. Though I like the 5 person dungeons and the bosses don't feel that generic. No more so than bosses I fought in WoW, but again WoW has so many boss mechanics if it didn't feel kinda similar/old theyd be using witchcraft over there. However whether it is intended or not, allowing my group in AC to pull 2 bosses together who FIGHT TO THE DEATH as we watched. Was amazing.
WvWvW is fun, but as dark said if a PvPer do tourneys and non world PvP, as its mroe structured. (especially since they will add more structured PvP down the line).
And dark didn't say much on it, but the main things you do "at end game" on GW2 is:
#1 have fun, combat is more "action-y" than most MMOs as you do dodge and have to move alot even as a caster.
#2 Farm items either through dungeons, crafting or go for the legendary item that requries so many materials it makes every Legendary on WoW seem like a daily quest.
#3 Farm cosmetic items and dyes, to make your character look pimpin.
#4 PvP
#5 Roll another character to see how different the characters really are. Playing an elementist to 80 was a blast. However sometimes hard. Started a warrior... ROFL I smash things blindfolded that would destroy my elementalist at the same level.