According to the manual,
As far as the playlist go, I've been able to move all the playlist that I've made in iTune to my Pre and I've been able to add to them through iTunes. Additionally, I've been able to make new playlist for the Pre in iTunes and drop songs into the empty playlist.
You can play music that you copy from your computer or stream from the Web in the
following formats: MP3, AAC, or AAC+ format. For files received as email attachments, you
can play files in the MP3, AAC, AAC+, WAV, AMR, or QCLEP format