I feel similar to most in that I don't have any real beef with Alignment as a means to describe a character, but once it starts affecting spells, classes, items, etc, it gets a little out of hand. To me, the idea of "detect evil" is be kind of like "detect pale skin" or "detect brown hair." Its a mechanical system that highlights something which would serve to simply describe who your character is, not be a strict framework. (I suppose I should mention that I haven't ever houseruled anything away, and have (and am in one game) played the "Detect Evil? Attack!" paladin. He's a little more intelligent than that, but the point is, I do use Detect Evil.
Flavor-wise, my biggest issue with alignment is that not all of them really make sense. I can understand Good, and I have my own opinion of Evil, but what constitutes "Neutral"? I find it impossible to think that any interesting character worth playing would actually be truly neutral, even if only on one of two axes. To me, a real neutral character makes me think of the Neutrals from Futurama. Not exactly my idea of an exciting, dynamic character.
On that, though, I did once play a True Neutral Soulknife who I thought was really neat, because it took an interpretation of TN that I hadn't seen before (doesn't mean it hasn't been done, just not within any of my games). As a psionic, he had this view of balance being the ultimate, and that existence is basically a zero-sum game. So, whenever an ally (or anyone) did something that he interpreted as a "Good" action, he would make note and attempt to do something "Evil" a little later on. Similar for Evil action, Lawful actions, and Chaotic actions, so his alignment seemed to be swinging all over the place.
(ps: free tibet)