TiVo is by far the best piece of consumer electronics to come out in a decade. You can watch all your favorite tv when you have the spare time regardless of your schedule. Never more will you mindlessly channel surf for something interesting. Why it has not been an overwhelming success in the marketplace will forever be a wonder.
As to video quality, at the top settings of compression it degrades original signal minimally if at all noticable, though like any compression based video source there tends to be more motion artifacts with high movement content (sports, action movies, etc). Of course with Directv already being highly compressed and all the interference with cable signals, it doesn't have much to work with.
One clarification though, the lifetime membership mentioned by Ras is for the TiVo unit rather than your lifetime. the yearly or monthly deal makes more sense, especially with potentially newer technology coming down the pipe like moxie announced at CES. The unit is pointless without the service
- TiVo changed my life - run dont walk to the store and get it.