Just had to book some flights for an early-fall trip to Podcast/New Media Expo as well as to Austin to meet with the BBM sales team. I've never been a fan of multi-legged trips, as I've never been happy with travel tools available to book them. This time, I used both Kayak and ITA's Matrix to find my options, and I have to say that the results are miles above what's available elsewhere. The big difference here is that these engines clearly are geared towards giving the user what they want. Instead of obsessing over having me on the same airline throughout my trip, Kayak and Matrix pull together the best times and prices for me, regardless of carrier. Finally someone's getting the idea.
Though I found Kayak's layout/interface and the flights it found to be better, these two tools will stay in my arsenal going forward (with a nod to SeatGuru, since I couldn't live without that knowledge!).