Like Talia, most artists that I've admired in art have been pretty neat IRL. Neil Gaiman, for example, was a total (ly exhausted) gentleman, even when my wife and I got our gush all over his dignity. Amber Benson was funny, clever, and patient with her audience's goobery questions and odd comments about her work on Buffy. R. A. Salvatore was extremely friendly and took the time to give me writing advice... I must have been ten at the time.
On the other hand, I honestly never liked most of Orson Scott Card's work. Ender's Game is all right, but I find the rest of it somewhere between cracked and half-baked.
There's probably a bit of confirmation bias here, probably also a weird effect based on the fact that I like most people and most books. In general, though, I find that I just don't like the way assholes write, and most writers I like turn out to be neat people.
You'll note that I've drifted into writers, rather than actors or musicians, which is probably part of it. I think writers, who are always creating their own material, put more of themselves into the work that I already seem to know them through. It make sense that I tend to like writers that I... well... like. I'm not sure the same is true of actors, especially screen actors, which might explain my attitude.
