Our sister site Lifehacker put together a list of ten app-based ways to boost your media center's potential, adding support for remote controls, remote TV scheduling, Hulu Desktop and more. My favorite: Ad removal. Suck on that, ad-supported entertainment! [Lifehacker]
If all you're doing is recording shows to watch later then it's not any more illegal than using a VCR.
Legal issues only become a problem if you want to start building a long term/permanent library of shows and/or start sharing them with your friends and family.
That's not to say recording off the TV is legal. Strictly speaking it's not. You're still making a copy you don't have permission to make.
Similarly if we interpreted the license that comes with CDs/MP3s and DVDs in the strictest sense. Then loaning a DVD you have bought is illegal and leakage from your MP3 player headphones can pass for a public performance.
Personally I stopped worrying about these legal issues a long time ago. When I can no longer enjoy the music, TV and movies I watch because of draconian DRM or legal restrictions I'll simply find something else to fill my time. Which is what everybody else should do.
So in the end the only people that lose out are the idiots trying to shake every single penny from our pockets. #htpcs