Well here are the few simple steps to make sure that when you need you’re object to get its ‘sharpness’ back you can.

1. Before you set the Z property and while the matrix3D is null take a copy of the objects matrix.  You can do this by accessing object.transform.matrix, note as soon as you set the Z property the matrix3D will go from being null to being set and the matrix value will end up becoming null.
2. If using a tween or similar to go between a certain value (rotation) and 0 then I found that unless you explicitly use the value 0 in the end tween function that it may set the end value as 0.0001 or something very close to 0.  This will not be enough, so in the end tween function I always explicitly set the value to whatever I want it to be at the end.  e.g. if my tween was something like Tween(this , 90, 0) then in the onTweenEnd() I make sure that the value is 0 (rather than just using the value passed into the end function – which may or may not be exaclty 0).
3. As soon as the rotation value is 0, then I set the Z property to NaN, then set the object.transform.martrix3D to null and finally I make the object.transform.matrix = the previously copied matrix.
4. As soon as you copy the matrix to the transform.matrix property you should see your object become sharp again.
5. Thats it .

Hope this helps a bit.

Anyway I got a Sin() mixed up for a Cos() and the following effect happened which I thought was quite a cool effect. Ignore the colours and its roughness it’s just a prototype swf but I thought I stick it up just to show the side effect that I never expected

Not Expected

Expected