March 1, 2010 - Portal Update Released
Updates to Portal have been released. The updates will be applied automatically when your Steam client is restarted.
Changed radio transmission frequency to comply with federal and state spectrum management regulations
Apparently from what I've read is that theres a new achievement and in there are radios scattered around now.
I can make a video where to find them all
Lotsa Info here about the achievement and the secret new radio transmissions