Pros: beautiful graphics/music, very social, huge world, tons of things to do, years of gameplay
Cons: monotonous sometimes, time consuming, addicting, can't quit suddenly because of parties, hard to get gil
The bottom line: Buy it if you like MMORPGs, free-form playing, and games you can play with your friends. If you like structured plots and permanent endings, don't bother with it.
This is a great game for hardcore FF gamers. It does require a lot of teamwork, though. After the first twenty hours of play, you'll be hard pressed to keep alive and get far without at least one other person in your party. This does make it very time consuming to find a party and to give them ample time to know you're leaving. It's not a sit down and play until whenever game. It is fun, though, if for nothing else than the social aspect. If you're more of a soloist, get a different FF game or Chrono Trigger or Cross or Legend of Dragoon or some other famous RPG. FFXI does have great visuals and music, so at least the effects don't get boring. The game play can get redundant when you're leveling at the start. It also gets very frustrating trying to raise enough funds to replace your equipment every few levels. This is where high level friends come in very handy. The magic spells look awesome, too, for anyone who wants to be a mage. ^_^ And finally, once you are a high enough level to explore it, the world is huge. It could take forever to see it all. This makes it easier to level up in the dozen or so jobs you could switch between.
Graphics - 10, each area is very different, pretty, and suitable for its location in the world
Music - 9, it gets old after hanging out in an area for a few days, but it is Nobuo Uematsu, it mirrors some older FF games (ex - Odeka de Chocobo), and it matches the area
Storyline - 2, there is a basic plot, and you learn a little more about important people as you complete quests and missions, but it advances very little past the opening movie
Gameplay - 8, you can switch between and level any of a number of classes, there are quests and missions that must be completed, and every time you play different things are happening and different people are on, it does get monotonous after being in one area for a while and trying to get some items can be extremely annoying, the fighting structure gets a little boring too as certain jobs have to fill certain roles and stand in certain areas, skill chains are awesome, though, once they're mastered
Replay - 10, every time you log on, new things are happening, new people are on, and there are a million things that need to be done, there are expansions that add tons of new events coming out as well