Well, the endgame is definitely NOT what GW2 is all about. It's much more about the journey and the game is geared towards exploration and exciting PvP that isn't Rock/Paper/Scissors.
There is also a lack of the classic 'holy trinity' of tank/healer/dps. Every class has it's own set of interchangeable skill sets that are used according to situation.
If you go into it thinking 'I've got to get to 80 as quick as possible and then do all the dungeons' you will be disappointed. The questing system is quite different from the usual 'go to A and kill 10 boars' type thing too.
Regarding the community. Well, all MMO's have their share of arseholes (WoW especially) but if it's anything like GW1 community it will be decent.
Picked up the following from another site, sort of covers a bit more info about Endgame:
Oh and here in even more detail.
Hope that helps Mart.