One of my regular online haunts is Resexcellence. They've got a huge library of appearance themes for Mac OS X. While I enjoy looking at them, I've never installed any. I imagine that it's fun and satisfying to use a theme you've designed yourself, or simply one that agrees with your own aesthetic sense, but I just like Aqua. I agree that some of the inconsistencies are annoying, but I'm willing to (begrudgingly) live with them.
So what's your take? Do you mod OS X's appearance? Have a favorite theme?