I've been using http://matrix2.itasoftware.com for flexible flight searching. From the few minutes I have been playing with Adioso, it seems even better.
Thought the same thing here. Usually the process needed to find the cheapest flight is rather convoluted when you have few date constraints: 1-choose a date/2-[wait a lot]/3-check price/back to 1. But with this... easily accessible data via graph/table, 4-5 clicks and you are done.