Thomas Hawk, the guy that wrote the in-depth test between his Windows Media Center box vs. his new HD TiVo has published a great article on engadget today called Ten things that Microsoft and TiVo must each do to win the living room.
In it are his ten biggest gripes with both Media Center and TiVo, and what they can do to produce the ultimate device. After reading about his struggles with a Media Center unit, his ten suggestions sound great, though some are certainly difficult (he calls for the creation of a TiVo-for-radio feature) and others are bordering on the impossible ("Media Center should be as stable and error-free as TiVo’s Linux-based system" heh).
On the TiVo wishlist, two gripes are about the discontinuity between DirecTV's TiVo unit features and TiVo's own featureset, which I wholeheartedly agree with. The "DVD in every TiVo" would be a nice addition as well, though I suspect content companies will never let it happen in the HD model.
I hope engineers from both companies are listening, as well as management. Thomas is an early adopter that spends thousands of dollars on these products and before you know it, his views will be the same as the mainstream as they get increasingly used to these products.