trshaner,
Thank you. It seems this behavior is quite normal, or at least common.
I always thought it's just a consequence of the file size, and would have never mentioned it until I read the report of the OP.
Yes, I know I can start working as soon as the spinning wheel disappears. Problem is, that I load the 1:1 magnification for evaluating sharpness, and so just have to wait.
But it can become a real drag when you have to go through lots of images and want to evaluate them all at 1:1.
Probably not much we can do about ...