Anyone using a prepaid SIM on an unlocked GSM iPhone?

[deckeda]

Anyone know if these phones on AT&T MNVOs would work on the AT&T Microcell? I'd guess not, only because it's not a branded "AT&T" phone at that point?

So, no Visual Voicemail, and MMS doesn't "work" except from another iMessage user ... anything else to be aware of?