There are release notes for the alpha software, but not a FAQ. You should be able to find the release notes in the same place you download the alpha software (I think).

The big feature that alpha 3.0 offers is playback of OGG and FLAC files. If you don't need to play those kinds of files, the "alpha" part of alpha 3.0 makes it something you don't want to just install on a whim.