I read a few pages back that some are having trouble with MMS. Mine is actually working fine on the Photon UX v2.2. No problem sending, receiving, or clicking directly into MMS from message notification button. It is a bit unstable with apps running in the background - some lag after the second MMS sent and I had to restart to retrieve the icons at the bottom of the All Messages screen. Ok so far.
I did have similar MMS problems with v2.1 though, and I think I can trace them back to one failed-to-send MMS. It took days to receive the timeout notification. I noticed the unsent MMS still sitting in my Outbox months later when about to restore from PIM Backup after flashing to v2.2 and removed it. Perhaps this might be causing the MMS problem other posters are having?
BTW, is it possible to make the Outbox folder appear under All Messages>Menu?