TiVo has now released a new Desktop Update version 2.3. Version 2.3 now costs $25 and will allow you to convert files to MPEG-4 or H.264. Basically, the new update adds support for your iPod, PSP, Treo, Nokia phone, and any other device that has support for MPEG-4 or H.264 files.
The other addition that the update provides automatic transfers of recordings to your PC overnight.
Go here for the update.
If I'm not mistaken this update has no support for Macs and only Windows 2000/XP.