So I've been caught up in yet another MMORPG, only this one has the extra benefit of NO subscription fees! That's right, a well done MMO that only costs you one flat fee for the game itself. No wonder it meets and/or beats Warcraft's standards of business success.
It's your standard MMORPG, skill-based (the more levels you get the more points to spend on skills), only more "minimized", but not really in a bad way at all. How it works is like this: All the towns and outposts and cities, etc., are where teh actual players congregate in. There are different districts for each community center to save on lag when they're full up. You can't fight enemies or have duels or be attacked or attack at all in these posts. You're there to meet up, gather, talk to NPC's, get quests, etc. It's when you go out into the exporable areas that things get different. You have your own little instance of the exporable area. It exists as long as you are out there and not in a town. All the enemies you've taken down while out there, basically reset once you go into a town/outpost/etc. You can take along party members, but first you need to get with them in a town, make up the party there, with friends or fill in members with NPC allies that will fight alongside you (big bonus for you loners, because the NPC's actually have competent AI, and a party of 4 with you and 3 NPCs can still take down a powerful target). Your standard choices are usually a tank, healer, and DPS classes. You can choose which NPCs you recruit into your party for the explorable areas, so if you play a healer, you can pick all other classes. Or pick the other healer and just be lazy. Etc. This mixing up makes the game very interesting. Makes playing solo a possibility, for most things.
There is a PvP element, and it's handled in the games many arenas. You can either go up against other parties with your friends vs. their friends, go up against an enemy with parties full of NPC's, or go up against a rival with a party of heroes. Heroes are special NPC Henchmen, like the NPC allies mentioned earlier, only you can pick-&-choose what skills their merits lay in.
You can also compete guild against guild, with the same types of battles. Your parties, whatever they consist of, can be in capture the flag games, obliteration (kill count) games, capture the flag stand (which is a variation of inverted capture the flag - you put your flag in a defensive stand and try to keep it there while the other party tries to do the same). Etc. It's not free-form PvP, it's not Realm-vs-Realm like in Warhammer Online (they copyrighted that term, by the way. So, trademark, registered, copyright, etc, Mythic/EA games).
Combine it all together, and you get a nice (not great but not horrible) MMO that has no continued cost. I purchased the Trilogy pack myself, that was $50 USD. The Individual games alone run $20-30 USD, which isn't bad, and I recommend Nightfall if you're only interested in one.