According to a list I found, it only supports:
VIDEO
?MPEG-1
?MPEG-2 (PS,TS)
?H.264/MPEG-4 AVC
?MPEG-4 SP
MUSIC
?ATRAC (.oma .msa .aa3)
?AAC (.3gp .mp4)
?MP3 (.mp3)
?WAV (.wav)
IMAGES
?JPEG
?GIF
?PNG
?TIFF
?BMP
I wouldn't be surprised if someone hacked some divx playback (or other formats) in the future. However, most likely Sony would have to purchase a license for Divx playback. (Not sure about licenses)