I'm really interested in getting it, but what all do you do in it? I assume that you hunt for monsters (as the title obviously suggests), but what more do I need to know?
That's pretty much it, to be honest. But I'll be darned if it isn't fun.
It's probably worth noting that this game doesn't provide you with some of the luxuries that typical action RPGs tend to have, such as the ability to lock on to targets, or generous hit detection. You have turn to face your targets on your own, and you have to be really precise with your hits (All monsters take varying amounts of damage based on where you hit them, the head typically being the best spot).
It's also relatively high on the difficulty scale, as it's not uncommon for the monsters you deal with later on to be capable of killing you in one to three hits later in the game, and they're not exactly easy to dodge, either.
Those points have come understand criticism by many people new to the series, but they just make it a more fulfilling game experience, IMO.
The online, as far as I've experienced, is flawless in regards of how much lag there is and such, too. It can get rather irritating if you get grouped with bad players, though, as three deaths total equals a quest failure, plus the game doesn't reward extra for anything other then not dying, which can result in cowardly or slacking players sometimes.