Any transform degrades the image, and the effect is cumulative. The only ones you get away with are straight 90 degree rotations.
The way to avoid (most of) it is to work with smart objects. This essentially "wraps" the original and keeps it unaltered, and all subsequent transforms still refer to the unchanged original. This way you can do multiple transforms in succession, and still only have one final transform event when you finally rasterize the smart object.
As @D Fosse already stated any transformation (with some exceptions like the 90˚ rotations) has an effect.
The screenshot shows Polar Coordinates applied twice to a checkerboard image; once »Rectangular to Polar« and once »Polar to Rectangular« – the effect is not equally terrible in all areas but it seems noteworthy.