A lot of buzz over at Howard Forums about Straight Talk phasing out support for the ATT network. Straight Talk has stopped selling an ATT specific SIM card (although their generic unlocked GSM SIM should work on the ATT network) and might eventually leave ATT altogether and become a TMO partner exclusively for GSM support.

If you are on ST right now, and using their ATT network access because the TMO network is simply unacceptable for MVNO coverage, you should keep a close eye on this development and be prepared to switch (Net10, Redpocket, etc) should this become official.