Specifically, I miss the function to get back to a previous window by some shortcut. It seems, SnapR. does not have a fixed order of windows at the same position.

Did you try the app? When you have tons of windows those expose items can get pretty small. Expose can not just bring a window up front, you have to go search for it in expose. With this app you can cycle through your apps w/o having to use expose... without ever changing your desktop at all. Windows are cycled through and you choose which you would like and it is brought frontmost. Come on bud, we all know about expose etc... use the app and then make a decision. If expose is good for you, great, if not here is one option of many. Review's are more helpful than comments. Give us a positive and negative so users can get an idea of what the app is like, its' shortcomings and benefits are what makes MU review feature great. I personally have a small gripe w/ the way the shortcuts are set but then again this is just the first release since 1.0... It's still an infant.