Apple has rolled out iOS 4.1 to developers. First significant difference is the signal bar. According to Apple previously, there is a mis-calculation on the signal bar and they mentioned they will rectify it. It seems that they have already done so.
From Engadget, you can see the signal strength has “decreased” using the same network.
Other than this, Gizmodo has detected the firmware differences on the modem
That little tidbit aside, it appears that the modem firmware has gotten an update as it’s now version 02.07.01.
So, if you are a developer, you should know where to get this update.