I like both, although ITA is superior. Hipmunk is what I recommend to people who don't want to learn to use ITA. On the other hand, I think Hipmunk is great for searching for hotels, and there aren't many competitive alternatives in that area. If you want to learn to use ITA, I have a little guide on my blog, along with reviews of Hipmunk's flight and hotel search features.

http://hackmytrip.com/2012/01/introd...-to-using-ita/
http://hackmytrip.com/2012/04/update...-hotel-search/
http://hackmytrip.com/2012/03/update...flight-search/