Photoshop :: Canvas Rotation - Images Appear Soft?

Canvas rotation is a great tool, but something bugs me about it: As is commonly known, Photoshop offers pre-set zoom levels. By that I mean 25%, 33,3%, 50%, 66,7%, 100%, et. In other words: The zoom level Photoshop jumps to when using the + or - buttons on the keyboard. If an image is in it´s normal orientation on the screen, it appears sharp at all zoom levels. This changes however with canvas rotation.

Rotated at 90°, 180° and 270° the appearance of sharpness is maintained at all zoom levels. But with a rotation in between those values the appearance of sharpness is maintained only at 33,3% and 66,7% zoom. 25%, 50% and 100% make the image appear soft when combined with free canvas rotation.

Could it be the graphics card/driver having a problem with the image represantion while canvas rotation is used? And if so, what kind of graphic processor/driver would be able to maintain the appearance of sharpness at all zoom levels, while canvas rotation is being used?
 
Before I come across as being nitpicky: I´m mainly using Photoshop for illustration, which means a lot of freehand sketching. Being able to rotate the image area is therefore very important for me, and at some point this soft appearance of an image started to slightly annoy me because it´s slightly blurring detail. I guess it´s the same with seamlessly zooming in and out: At odd zoom levels the image becomes kinda soft as well, even without canvas rotation.
 
A little excursion into the past, to clarify this issue further: Let´s wind the clocks back to pre-creative suite days. Back then I noticed something strange with those pre set zoom levels in Photoshop. The image appeared perfectly fine at 25%, 50% and 100%, but had jagged edges at 33,3% and 66,7% (as if overly sharpened), which basiclly forced me to work only with the zoom levels mentioned first. Now this problem is gone, which I guess is mainly due to improved graphic drivers (if not: Let me know, I´m always willing to learn).