Thanks for the link. I often don't care if I arrive a day earlier or later, and the quick day switching is something I miss in Hipmunk. Kayak is alright, but momondo seems to do an even better job.
Do check the list of sites they search:
http://www.momondo.com/we-search/
I don't remember how I stumbled upon these guys, but generally their flight results are the cheapest. They don't do too well in hotels (I tried US ones) though.