Achievement Hunters Unite, Replayers Disperse.
I can also imagine people without these common interests loving the game, at least for a while. The boss battles are so much more that the slash and dash monotony I normally find. There is innovation all the way through, from the health and mana fonts to the choice of levelling up your evil or good sides that leads to more tactical awareness than a common strategy game.
The only real problem I can find, and it's not really a big one at that, is the fact it becomes slightly unreplayable. After you've done it once, the only thing you can look forward to is going through again with your supped up moves and hit those achievements impossible to do in one run through.
This brings me back to my original Review Deck. If you love achievement hunting, I assume any game is the one for you, but in this case your gaming experience will last much longer than those just in it for the story.
Overall then, if you think you'll want to replay it, buy it. If not rent it, or at least get it via trade in because in all honesty, this is game I wouldn't want you to miss.