The messaging button (number 4) on the right side of the Wing allows you access the Messaging application directly with a single press, holding down the button will invoke the Voice Notes application. I remapped the messaging button hold function to use VoiceMinder from WebIS which emails me my voice notes, since Exchange ActiveSync does not synchronize Notes (you have to connect up to a PC).
Another feature the message button performs is cycling to mailboxes while your are in the Messaging application. I had been using the D-Pad right and left actions but this gives me another navigation options.
BTW; if you want to change your button to application mappings, all you need to do is use the start/settings/personal Buttons application. The only button that has a press and hold feature is button 4.
I have modified the default on button 3 to launch the CommManager application and button 4 hold to launch the VoiceMinder application.