I posted test results from comparing the FlySight GPS to the GT-31 on my blog at boardsurfr.blogspot.com/2013/09/flysight-better-gps.html
The FlySight appears to be more accurate, especially in turns. The blog post includes a link to a zip archive with the test data near the bottom, in case anyone want to look at the data.

It would be great if the FlySight could be added to the list of approved devices for the GPS Team Challenge. It uses the u-blox 6 chip, and custom devices based on this chip are allowed for records on GPS-speedsurfing.com.