I'm sure the issue with transformed layers, becoming blurry, after being transformed has come up a few times. One way I try to get around it is to make sure that the values in the transform window are pixel perfect. But I for some reason I find that it still blurs. I would guess that is because the transformed object is off by a decimal that is not shown.
I think it might help if it were possible to enable a pixel snap. (if that is the correct terminology) Maybe working similar to the snap rotation. except it snaps the transformed object to the pixel grid.