I went to HowardForums and got my wife's 3Gs MMS working in about 10 minutes. Incredible.
It consists of running one command line, downloading one file, and having iTunes update the carrier file. I did a restart and MMS was there. No settings to set - nothing. It just worked.
We are in Vegas and I sent 3 MMS from her iPhone to my bold and I sent 1 back. Worked like a charm.
Hopefully it will stick. We are on a PC with iTunes 8 and she has 3.0.1 on her 3Gs. We are on the family text plan.