I went through the differences documentation for iOS 6.1 beta 2 and noticed nothing very significant. However, Apple doesn’t always put things in there. For example, below you can see that in iOS 6.1 beta 1 a few days ago, Panorama was all messed up in my camera, however in iOS 6.1 beta 2 it has been fixed. The above screenshot was pointed out by the documentation. A new button is found with Settings under Advertising (Settings > General > About > Advertising) labeled “Reset Advertising Identifier.” Here is the description via the Apple docs:
In iOS 6.1, a new Reset Advertising Identifier button has been added to Advertising Settings. This button resets the Advertising Identifier so that future requests will return a different value.
So basically, you can reset your identifier at anytime. Why would you want to? Good question. But you can.
Another thing noticed in the 2nd revision of iOS 6.1 is a new Pass in Passbook. Before you would be given the blank screen shown below on the left, but now you are given a Pass with information, shown on the right. You can delete this Pass just as you would any other by clicking the Info button in the bottom right and then the Trash icon in the upper left.