I had been eagerly waiting to get done with my current project so I could upgrade the ADT/SDK for android to r12. I'm glad I waited.
When I fire up the emulator after updating I get the following screen.
Update : Thankfully, it's a known problem http://code.google.com/p/android/issues/detail?id=18299
I had used -scale 0.5 to get an emulator window that fits my laptop screen. The simple workaround is to just use -scale 0.49 until the r13 ADT is out.