Yeah, Guild Wars is sort of an MMORPG. You do not pay a monthly fee but you pay for new content if you want to. The big thing about this game is that it is centered around guild vs. guild PvP battles.
By the way, mark me down as a gamer. I am not currently playing anything at the moment though. I am kind of in a gaming slump.
While it's true that GW has a PvP sytem it's a misconception that PvP is the greater part of the game. The PvE world is huge, 90% or more of the content is PvE only and I'll bet my Warrior/Necro that 50% or more who play the game would not if it weren't for the PvE.
I have zero PvP interest and still have over 250 hours in the game, it's that good. I put it in the action/rpg catagory with an online aspect. You can totally ignore people and do the whole game with hired henchman although some missions and quests are easier with PuG's but not by much. There are one or two missions that must have people but you can skip them and get the rewards elsewhere.
There hasn't been any new pay-for content yet although a new free zone and dungeon, Grenth's Footprint and Sorrow's Furnace has been released just recently.