About the GUI, I was looking at the other thread about PyPianobar, and I saw the part about the library for it being as large as 44 MB. That might be okay for N900 users, but I checked the free internal memory on my device just now and I only have about 45 MB left total (!).
One question about the command-line version....is there a way to get it to store login information? I found the config file in the pianobar directory and edited it, but it didn't seem to make any difference, so I'm guessing the application doesn't really use that file (?).