Thomas Hawk has a lengthy review of a new HD Tivo vs. Windows MCE. He's been a TiVo user early on, then used a Media Center PC hooked to a plasma for a couple years before upgrading recently to a Hughes HR10-250.
He compares and contrasts all the little differences between what you can do with an MCE box vs. what you can do with an HD TiVo box and in the end the TiVo wins hands down for the incredible picture quality:
I pushed play on my forgotten old friend that wacky peanut shaped Tivo remote. This was something. And right there at 9:12 p.m. in my living room was the most beautiful picture with the best sound I had ever experienced in my life.