I will soon be a new TiVo user. I find the Home Media features great, especially the music. All my music is encoded in .m4a or AAC. Will TiVo play AAC files or will I have to have my computer convert all AAC files to MP3 overnight?
The TiVo itself can only play MP3. Some of the 3rd party music servers can transcode other formats on the fly so you don't have to have MP3 copies of everything. I know AAC can be transcoded on a Mac using TiVo Desktop and LAME, but I'm not sure of any solution on Windows.
J. River Media Center can do on the fly transcoding of (most? all?) formats that it supports. I haven't used it personally (although I may give it a whirl in the near future), but it seems to be a pretty nice program and has a fair sized community around it.