If you have problems with audio while changing receiver settings at runtime you can try to apply this patch: https://gist.github.com/664132 (this fix has been included in GNU Radio since December 2010).
I have also made some modifications to the gr-qtgui code in order to enable grid, have nicer colors and take up less vertical space to better fit on laptop screens. These changes are available in this patch: https://gist.github.com/668462. This is not mandatory though, just part of the experiment.