I have both a Tivo HD and an AppleTV. I use both of their respective iphone and iPad apps, tho not as primary controls. For the Tivo, I use their app to remotely schedule recordings and for the pop-up keyboard when I'm doing a search. Otherwise it's the Harmony remote. Pretty much the same with the Remote app for iOS. Works great, but I usually only use it for text entry and the occasional music or video library search. I do find that I use AirPlay to shoot video from the iPad to the AppleTV quite a bit.
Anybody use iPad/iPhone apps to watch TV or remote-control your TV? With or without an Apple TV device? I'm looking to overhaul my TV situation, and I'm curious if you find any or all of these things worthwhile when it comes to TV watching, and whether it has changed how you watch TV much. The mirroring (shoot video from an iPad or iPhone to your TV instantly) looks especially interesting.