Bandwidth delivers SMS over SMPP. Initially the MMS launch was due for mid October, seems they launched it ahead of time.
In the following weeks you'll see lots of different providers announcing their MMS capability.
Bandwidth should get the credit for their brilliant work.
Lot of effort by a large crew of committed developers and the helpful participation of our carrier partners are what brought Twilio MMS to market on US phone numbers. Were MMS as easy as wrapping another product in a HTTP request, I imagine it would be a more common offering.
Want to make sure the effort of the Twilio engineering crew is given its due.