I understand there are going to be 5 cities getting LTE on the 15th, but for whatever reason they turned up Kansas City yesterday or today. I can only guess it's because the corporate headquarters are here.
To get the MSL, I had to call and ask them since I couldn't just turn on the LTE feature. I don't know if they'll roll out an update on the 15th so that everyone can, or if they just will handle changes one at a time. Mine was disabled from the factory, but my wife's S3 enabled LTE without any issue.