in my experience its ui is not perfect yet, and crashes often times... you will know when you get it and start using it.
( im talking about buzz player classic, not flac player which might be much better )
I use buzz player "classic" because I have iphone 3g which does not support other buzz player version
if you have 3gs or newer. you might like Flac player from app store, I cant use it because it keeps crashing on my 3g
if you Jailbreak, you can get both flac...