This is really nice, but they haven't solved the following problem: sometimes you need more information from further on in the process in order to choose your dates. For some types of trip, the most important thing is a combination of departure time and price; you want the lowest price as long as the departure/arrival is within your acceptable range, and then you want to work 'backwards' to pick dates based on that.
I don't know of any airline booking process that accommodates that use-case well.
Hipmunk lets you search for flights with a certain date range and pick the best flights from that, and there's also a "pricegraph" that sounds like it does exactly what you want by showing you the cheapest prices within the next 90 days.
