I'm using VisualBoyAdvance w/ the fast kernel and libsdl from externe.net. It plays regular GB games at nearly full speed (I pretty much only play RPGs, so a little slowdown doesn't bug me) I don't recall having needed to do anything special to get it running or anything.
I also have snes9x running no problem. Amazingly enough, it's even faster then VisualBoyAdvance. I followed the instructions on externe.net, (I think the special libsdl is the thing that really makes it work well) and it just works. Works well too, I might add.
-ross