Without getting our hands on it we cannot give accurate feedback, however as a daily iPad Pro user I can say the Stage Manager looks like a complete waste of time. Its basically split view except each window is smaller and the dock takes up permanent real estate. On an 11" model this would be a UX nightmare.

Having multiple small windows open simultaneously isn't any better than the current solution because you still have to expose them all out of the way to find the one you want, just like swiping up on the home bar currently.

I don't have any problems with the current state of things and can drag-and-drop files from emails to cloud storage or check some stats whilst typing without issue.