Drag a bunch of TIFF scans to Acrobat. It asks, "Adobe Acrobat can create a single document from all the image files you are opening. Would you like to put all the image files into one document?" I say Yes. A number of progress windows are shown. This will take a while, so I switch to a browser window... and less than a second later, Acrobat seals focus back to show me the progress window. So I switch back to the browser window... and it steals it back, ad infinitum, until Acrobat is done some minutes later. During the import process, I can see that only one core is being used. I have 4 cores. I would like to use my computer... but Acrobat thinks it's more important to tell me it's doing the next page.
During one of these attempts to use the browser window, Acrobat "caught" a CMD-Q that was meant for a text editor. It showed a dialog asking me what it wanted to do with the open document, but it had a beach ball on it. After finishing the import, Acrobat was still showing me the save dialog, but it would not react to the clicks (still a beach ball). CPU went to near zero. I had to force quit Acrobat and lose my work.
Please, this is really buggy behavior. It's not even using multiple cores and I can't use my computer until it's done.