Well, it took me 5 hours just to beat the first full level. But that's because you die really fast and the learning curve on the game is retardedly hard.
But, from what peopel have told me they get a good 50 hours in PER runthruogh, most peopel do 5 - 6 runthroughs before they get completely bored with the game. But it's not like games like Mass Effect or Fable or KOTOR where you have the "good", the "evil" and the neutral storylines. The game is dynamic and changes greatly just depending on what NCP's you talk to, who you save, what enemies you kill, so on and so forth.
And one of the greatest things about it (well, not at first) is that the more you die the harder the game becomes. And it gets significantly harder.
Once you finish the main story you can start a New Game + which keeps all your shit. Stats, items, magic, then boosts the living hell out of the enemies and bosses in the game.
Character customization isn't the best (start with one of eight classes - the only difference between them are your starting stats and the equipment, with 4 of the classes able to cast spells - 2 healers, 2 nukers) out of the gate, but it's a game that's actually fully customizable with your stats. So you could start off as a priest and just mash str and vitality and become this uber healing tanking beast. Or you could go Royalty and keep your stats even and be a jack of all trades.
The online / multiplayer of the game is weird. It's not the same multiplayer that you're used to. You can use these items in game that let you be summoned by other players into there game and you help them out with the level they're on. Or you can invade their game as an enemy, hang out with the other enemies on the level and gank the player, kill him, and loot shit off his body.
And I'm fully fluent in ProTool, CoolEditPro and Ac!d.