I have compared boot times with custom Linux kernels (which I helped program, specifically drivers) with versions of _embedded_ Windows. When we add needed support features to Linux to match what comes with Windows... yeah, not all that different. Sure, if we compile our Linux kernel disabling a bunch of features we can boot in 1/10 the time of a standard embedded Windows system. But we need those features to make a product. We're not out to evangelisize about an OS. Our product makes us more money if we don't have to pay a license fee to MS. I am guessing the same for Tivo - they don't want to pay $$$/unit to MS when Linux works just as well.