They're just, you know, so repetitive. In my experience, definitely on Normal (haven't finished the game on any higher difficulty setting), killing a boss, even the final one, is just a matter of using your normal killing style - for ten minutes straight, while not dying in the process.

Rather less challenging and satisfying than in Diablo II - emotionally less satisfying, too, as the story doesn't go as far as to have real personalities or back stories for the big bosses, and if the bosses should happen to have any particular characteristics in terms of immunities or special weapons to watch out for, I've never noticed it, so you can't really plan strategy. Whereas I've killed Diablo, I don't know, a dozen or so times with various characters on Normal and Nightmare, and each time it was a challenge and satisfying when he finally went down (particularly with the Sorceress' commentary when he's dead ). That's less the case for the other bosses, and Baal is just annoying, true, but still.