[tricol]

I've used both and Sky is much better than Tivo for BBC iPlayer as it first downloads the programme instead of streaming it so making it much better at FF and REW etc. The old V+ boxes are also better in that respect.
Sky has a much slicker and easier to navigate 'planner' (My Shows) interface with category groups such as News, Sports, Kids, Documentaries,A-Z being automatically assigned to recordings rather than lumping them all together as TiVo does.
They both have pros and cons, TiVo's main advantage being the 3 tuners if just used as a PVR but the convuluted menus and clumsy interfaces let it down along with it's BBC catch-up implementation.