Well, there were signals that something would change as soon as Apple launched the App Store for OS X. I think having signed developer ID's, with the option of allowing unsigned, is an OK step and might even bode for a more open iOS platform ... down the line.

All in all, of the two ways it was likely to go (allowing only App Store apps by default, or allowing only signed Apps that meeting certain criteria), I think this is the much more palatable one.