The story line is quite nice. things are well balanced. PvP can be done within close arenas maps only (so you can't be PKed). Cities are the only place, beside arenas, and your group when outside, where you can meet other players. When exploring, you are with your group (players/NPC (8 max)) only, PvEing.
GW mainly focus on teamwork and skill management, not who's using the best gear. Which is what I like. Ohh and you don't have to pay per month and your chars are never wiped.
Go watch some vids on youtube.
Ohh, and you can buy any GW EXCEPT eye of the north (this one is an expansion, not a stand alone). Once you have one game, you can buy the others online. They will be "activated" on your account and everything will install itself automatically when you enter a zone. So you don't have to worry about reformating or deinstalling, as long as you keep an installation CD. Even there, I think you can dl from their website.