This is disappointing. With all the data they now have access to through the ITA purchase, this is still much worse than what I can achieve with ITA Matrix (http://matrix.itasoftware.com/).
Love what you've done with Hipmunk, it's a fantastic resource to use with flights originating in the US. Sadly it hasn't given me much joy with my European or African routings.
Just curious, what can you achieve in matrix but not google.com/flights? (if flights is available for the start/end points).
Check out the routing codes that they support. It's like regex for flights.
Flights from almost all airports Google flights doesn't even supprot some of the major international hubs, Tokyo, Singapore, Hong Kong all not available.
Except speed. I love Matrix, but it's not exactly snappy.