There is finally a TiVo Desktop software for the Mac from TiVo... but it doesn't include TiVo ToGo, the ability to transfer shows from your networked TiVo to your computer. And it doesn't work on Intel-based Macs. But it's something, I guess.
Still, there is a logical paradox at work in some of these compatibility issues: If I had a Windows Media PC, say, I wouldn't need a TiVo. I'd use a Windows Media PC as my DVR. I use a TiVo instead of a Windows Media PC because I like TiVo better. Why punish me for that?