It would be nice if, in addition to the statistics we can already view for a filtered set of hands (e.g. Total hands, total won, bb/100, vpip, pfr, etc.), we could have the standard deviation of our net won. This would give us a an idea of how high variance our play is.
There are also other summary statistics that I would like to calculate, but apparently a mass export feature is already in the works. Being able to simply export the contents of a filtered set of hands, to an excel spreadsheet would be pretty great, and definitely increase the utility of the program for me, probably more than any single other feature.