The Mezzanine

Well, I did say trying to get the same kind of thrill. :) I can see him hero-worshipping Angelus at first as the role-model of a vampire, someone he should copy and live up to. But after a few years of that, he'd have an epiphany that actually, all that slow psychological torture stuff was boring, and even as a vampire he didn't have to do it.

He could do his own thing instead, and mock Angelus instead of trying to imitate him. Much more fun. :)

Mind you, on a similar note I have a suspicion that he isn't annoyed at Angel's actions in S2: he's annoyed at Angel himself, and so whatever Angel did would be wrong.