Beats Momondo hands down.
I'd never heard of Momondo, so I just checked it out.
Hipmunk's UI is WAY better for me trying to pick flights. I don't care that I might save $10 or whatever, as much as avoiding 8 hour layovers, or leaving at 5am. You can't easily tell any of that with an interface like Momondo's (which is just a pretty version of every other travel site).
Have you used Hipmunk? It's NOTHING like that at all.
Those sidebar features are the same on every travel website, except Hipmunk. The linear bar graph display of flights is, for me, infinitely superior than a data tabel that I can drag sliders around to change the wall of text. It takes me a glance to see that there are great options or shitty options on a given hipmunk search, even on my iphone. Momondo and basically every other site require significantly more cognitive work on my part to piece apart their text boxes full of information to figure out if that flight is a good fit for my needs or not.
Hipmunk's UI is WAY better for me trying to pick flights. I don't care that I might save $10 or whatever, as much as avoiding 8 hour layovers, or leaving at 5am. You can't easily tell any of that with an interface like Momondo's (which is just a pretty version of every other travel site).