I had an S1 UK Tivo for many years (hacked to get listings over broadband and with the webserver allowing you to schedule recordings over the internet) and still miss it... The UI is just second to none. In the end the lack of HD and the extra encode/decode process just killed the picture quality too much for me (even with the Mode 0 picture quality hack)
Makes Sky+ look pre-historic, even with the new HD EPG
. Media Center comes close - but still isn't as good.
If only Sky had done a deal with Tivo after their initial joint-venture in launching the S1 in the UK. The Sky channel line-up (50+ HD channels) with the Tivo UI would be brilliant.