I like the way his character has evolved so much since he first appeared as Buffy's would-be Watcher, who was tiresome and pedantic and "screamed like a woman" at every turn. (Mind you, the latest dark downturn is disturbing, as no doubt it's meant to be...)
I see a distinct parallel between him and Cordy in the way they've developed from near-caricatures on "Buffy" to real, caring human beings on "Angel". (Not to minimize the fact that they've both been incredibly good-looking throughout...)