I love TIVO, but it does have minor quibbles.
The 1080i image when compared to other devices PS3, Vantage and Draco Freeview is soft (slightly).
The main menu is SD. Channel change is sluggish. It won't play WAV files over the network and other quibbles that make it just shy of perfect.
The reduced component resolution was a real pain - so in the end I bought a Slingbox 500 which accepted HDMI and worked perfectly.
I thought you can lock the resolution to 1080p with the button on the front panel.