Well you came to a GW forum so you'll be getting some good opinions.
GW is different than all those games. Grind is practically non-existant, the game doesn't keep you in that level up mentality. The level cap is relatively low compared to other games, 20, below that everything you'll do can be considered a tutorial, when you reach level 20 that's when the game will really begin.
My opinion: yes it's a great game. I like MMO's but I never could really keep playing one for more than a month, it ALWAYS got boring. I've been playing GW for 2 years so you can see for yourself.
It generally won't get boring. There's a ton of stuff to do, all sort of elite missions and dungeons, and everything is playable through Normal Mode and Hard Mode (with increased rewards and other bonuses of course). So you can be kept in PvE a long, long time and with 3 campaigns and one expansion pack, trust me there's a lot to do. Even I haven't done everything.
PvP is nothing compared like other games, this is 'real' PvP. Not gear dependent, not level dependet, time>skill doesn't exist, in fact, it's the other way around. If you like it, you have the option from the get-go to create a level 20 toon with maxed stats and equipment strictly for PvP so you can jump right on it, you'll start off with the very basic stuff though. You can unlock those from both sides of the game however.
The combat system is very different as well, you'll notice that as soon as you get ingame. You only have 8 skills in your bar at any moment, but that is so you can strategize and create very different builds. Sinergy between skills and your party setup is key in GW and you'll find it out pretty quickly. It's more action focused as well. Also the dual profession system allows you to combine very different stuff to create unique builds and cover so much, I really don't know how to explain this to you.
That's all I can think off. Welcome to Guild Wars btw.