ITA is probably the most underrated travel app on the Net. It's my favorite, cleanest, and also the most powerful tool for searching for good value flights (you can also find flights that will net you maximum miles that sites like Orbitz don't make easy, even with ITA powering the backend).

I think Hipmunk is facing an uphill battle. I don't want to be a naysayer because I want them to do well (and thereby have more choices), but ITA spent years and years to get the kind of buyout they're getting now.