I have no particular love of the alignment system. I don't find it particularly elegant, and I don't think it does enough to encourage the players to role play.
The primary reason I've never abandoned it is that most peoples problems with the system seem to have more to do with thier own beliefs about morality, than any particular failure of the system to contribute to the game.
It always seems as if the most vocal opponents of the alignment system are those that want to play thier characters as Chaotic Evil (or at least Chaotic Greedy), but don't want the label 'evil' applied to thier actions for whatever reason. And generally, player who don't want an alignment system are hoping that it means - "There won't be any consequence to my actions."
It's always annoying to me, because I really don't believe that the alignment system adequetely reflects real problems of good and evil. But every time I make that claim, some player comes along and justifies that the system can indeed be applied to real people in meaningful ways. For instance, the alignment system invokes a enherently ordered universe of absolute moral principals. The alignment system therefore espouses the belief that the universe is an orderly place. Invariably, when some player comes along and says that he doesn't like the alignment system, it always turns out that the fundamental reason is that they don't believe that moral principals are orderly absolutes or that real people have any such beliefs. Which makes me want to pull my hair out.
So I don't ditch alignment because it would just be too much work for too little gain, given that the system by its very vagueness tends to be more broadly applicable than you would first think.