I wasn't able to find this in the FAQ or in these forums but for some reason, I can't seem to receive picture messages.
Regular text messages come in fine.
Picture messages (MMS) doesn't.
It just seems to stall at "Downloading"
fyi, I've got 4G unlimited running on an Android phone using ICS.
I set a test message from a fellow tmo user's phone also running Android though it doesn't seem to matter the source.