EDIT: Whoops, meant to hit cancel in the iOS app as I wanted to write a bit more but didn't have time… I'll leave the message as it stands.
Also, the screenshot I gave above is a pretty tame example. Compare it to another search where there are more airlines in similar price ranges - http://i.imgur.com/e7VJq.png
As someone who lives in a city that's always one connecting flight away, I can't tell you how many times I've almost booked a flight only to realize the one that's $5 more on the same airline connects in a city more on the way and with less layover time, and Hipmunk does a far better job of communicating that to me then a traditional list.
That being said, I'm not using it exclusively yet (I usually check both Kayak and Hipmunk just to make sure I'm not missing something), but I really like that somebody is trying to do something different and (hopefully) enjoyable in flight search.