RELEASE 1.7:
first of all we changed a conception of free version of our add-on: the basic version is no longer supported, we introduced the demo version instead. Demo version has all capabilities of the pro version, but pack result is rendered in a separate window - it cannot be applied to the UV map. Note that the demo version still supports ‘Overlap Check’ and ‘Measure Area’ functionalities so it still has a practical use, not only demonstrative.
We introduced improvements to grouped pack algorithm - now the areas of particular materials should be more convex, like in the picture below:
Yes, you guessed it - it is an example of a render from the demo version 
Note the grouped pack feature is still marked as experimental - it means you can except further improvements in this area 
Apart from that following options have been added:
Post-Scaling Disable: do not scale islands after packing in order to fit them into unit UV square. Enabling this option is not recommended in most cases.
Automatic Area Measurement: automatically measure islands area after packing is done.