My one and only MMO-favorite is
Kingdom of Loathing. It's Pro:
1. Free.
2. Humorous and (sometimes) very thoughtful texts.
3. Not real-time in most senses.
4. Gigatons of items and content that got updated now and again;
and
5. Great people for chat in right clans (actually, chats are half of enjoyment for me here).
Contra:
1. Monotonous. (All battles are typical "hit monster with weapon/spell/skill, wait for round 2" deal. But there are much more than battles, and it can be automated with 3rd party applications).
2. Repeating. (If, for some reason, you'll stick to main quest, it will be very similar now and again. Still slightly different for different paths - and after finishing main you can select another path. Most of content still in "side-zones" though).
3. Crude-drawing. Is simple black-and-white gif art enough for you?
As for me, game (and community) is great to keep me 2,5 years here already.
