One weird quirk is that Sprint chose to bypass Palm's threaded messaging app for PictureMail use, requiring you to send the picture via the "Pictures & Videos" program instead. This only applies to the Treo 800w. Lame.
Thanks to NightRaven and Vetack, who were working on the WM6.1 ROM for the 700wx, they figured a way to enable the built-in MMS capabilities using Palm's program. Next, Ebag333 applied this new trick to the Treo 800w and we now have a working version with a simple .cab install. This makes a much more integrated system.
Video and audio clips are able to be sent as well as pictures, of course. Click here for the thread and a slew of other pictures of the app in action.
Great work guys!
Small Correction: You can send multiple images and a text in one message.