UPDATE 3: Pretty much confirmed now. No more MMS for AT&T. Also, iTunes 8.2 Pre-Release 2 blocks editing of the carrier file. No more tethering.
UPDATE 2: Received this: "eems as if they stopped people from being able to tether and get mms by altering the carrier settings... people who changed theirs at the start can no longer access it.." Let us know what you're experiencing with MMS on Beta 5.
UPDATE 1: This may only happen for those doing clean installs (not restoring from a previous backup) so if MMS is vital to your iPhone 3.0 dev work, that may be the route you want to go for now.
We're getting some early reports that iPhone 3.0 Beta 5 now hides MMS functionality from AT&T users (see Beta 4 and 5 comparison pics, above). Previously, buttons and settings for MMS were present, though not enabled by default, though hacks allowed MMS to be turned on for AT&). Now, however, all visible signs appear to be gone, and it's too early to tell if hacks may still re-surface and re-enable them.
Anyone else seeing this?
Note: iPhone 3.0, MMS was never surfaced on some carriers like Rogers (Canada).