Besides the uses of the Fn key that have already been mentioned, another good use is to hit Fn + RF (the red stylized R logo key) which will bring up a dialog showing you the firmware version on your REDFLY as well as MAC address, etc.
Another option that is not well known is that you can simultaneously hit both the buttons on the bottom of the Touch Pad and that will change your cursor into the 5-way navigation mechanism that is present on many phones. Unfortunately some users found that if they closed the cover on the REDFLY just so, they activated this functionality without meaning to, and it was confusing when they then saw this different cursor. So in our next release we have changed the keyboard mappings so that you get this functionality by selecting Fn + 5 (not the FN5 button-the actual number 5 key) so that this can only be explicitly enabled.
There are other super secret things you can do with the function key, but of course they wouldn't be secret if I told you about them.
Okay, mostly kidding about that last part, but there are features that we plan to provide in future releases that will take more advantage of this key.
-Laurie
Director of Engineering
Celio Corp | REDFLY