I don't think most people would have issues playing ogg files. At least, I'd hope not. I'll probably just leave them as mp3 though. Some of them are already ogg files, but I'll probably end up converting them anyways just to save on space.
I was figuring I'd have to batch convert everything down to 128kbps but now I don't need to do that. Excellent.
Between the music and my insane amount of custom SFX and voice acting I'll be doing this will end up being pretty big. I'm a little concerned about the entry limits for the SFX files. Luckily I can just remove all of the vanilla stuff when I get to it and cannibalize all 2,000 SFX entries, which I'm sure I'll need every single one of.
I'm not a graphics artist, but sound engineering and voice acting are my playgrounds.
http://www.youtube.com/watch?v=TT0LI8A4E10