Our 'next' branch now contains the updated gr_filter_design tool! Thanks to Sreeraj Rajendran for his fantastic work on this! Also, thanks to Google for supporting the work through the 2012 Google Summer of Code.
When you build and install the 'next' branch, you'll now get access to the updated design tool. If you haven't seen any of the discussions about it from the conference or anywhere else, check out this YouTube video describing it's capabilities. Below is a screen shot just taken of the version that's now a part of our 'next' branch:
Make sure to check out the examples in the GNU Radio source code (gr-filter/examples/gr_filtdes_*.py). These show you have you can programmatically call the design tool and have it return an object containing the filter parameters and taps.