I've used Tizi for about a week now and it's great! Fast set up, fast channel switching, live-pause, record and timed record and it all works brilliantly. The Tizi app for iPad is elegant and intuitive. As a bonus, I've found that Tizi works perfectly with Equinux's TheTube app on my MacBook as well.
Downsides? I'm lucky enough to be in a strong signal area so no problems there, but its portability is limited by the need for a strong broadcast signal. Visiting friends a little further from the same broadcast aerial and trying to show off my new toy a was a complete failure. Ah well. I don't think it would have been overly difficult to equip it with an adapter to allow an external aerial to be used - that's stopped another caravanner friend from buying one - but it is designed as a highly portable device.