Okay so Craig called regarding the GT31 Lock up issue. Turns out that the current firmware should avoid lock ups.
When you toggle to a screen you can hold the large button down for 5 seconds and it will lock the GPS to the screen you are on... Craig though that the toggle button got depressed while I was sailing and it locked down.
Speed Genie - set to 5 MPH or 5 knots - more to follow.
The SD card feature are too detailed to write about but sound cool ... you can overlay your sessions on Google Earth etc.
Craig also said that 30 knots was smokin and not that common.