After installing the latest AIR runtime I am seeing a lot visual artifacts in older AIR apps that seem to be related to BitmapData.draw() in conjunction with a transformation matrix. It pretty much always happens when applying a rotation or skew and it also happens with certain offsets.
Here is an example created with Nodewerk (Nodewerk):
From left to right: original, skew, rotation, offset
I sent a similar report to non-labs forum. In my experiences these artifacts only appeared on Flash Builder's AIR simulator. Didn't see them on Android or iOS device.