MMS works flawlessly for GSM users
AFAIK.
For CDMA, it seems people are able to send - assuming they have the correct info in the APN.
I was able to send out using the correct settings. I have not be able to receive, and I do not know anyone on CDMA that has been able to receive.
I swear there's already a thread on this topic, and your title seems to make me think you know of one