Yeah I'm getting the same thing on my n810. This 'bumpiness' seems to be the kind of pop you hear with certain (desktop) emulator sound plugins - I can't think of a better way to ID it. CPU usage is satisfyingly low and despite the poppiness, the sound appears to be coming through just fine. I'm guessing libao is the culprit for the popping? I wonder if the same issue appears in os2007
EDIT: pianobar seems to make any text input into the terminal after pianobar was exited (Ctrl+c) invisible. Weird.
also - the link you provided for pypianobar has a single quote appended to the end
EDIT2: GUI doesnt seem to work. Can log in (characters for username/password don't show up), see my channels, but it doesnt seem to play music. Play button will switch between play and pause, not doing anything. There is a static song title, author and album. I hit the plus button and it seems to stick there. This could all be because I installed the pyqt packages from extras-devel, but I don't think that is the case