#1. Prevent applications from stealing focus. As an example, while I have been typing this blog entry, iTunes has stolen focus on me over a dozen times to tell me that is a processing a new directory while adding files to the library. If I minimize a program to the tray, I want it to stay there until I restore it or flash the tray to notify me that it has an important message for me. Please behave and honor my requests. I'm only picking on iTunes at the moment because it keeps driving me mad in the past 10 minutes. I accidentally hit the space bar when iTunes popped up unexpectedly and canceled my music import.
#2. Kill off
modal dialog boxes that prevent using a multithreaded application - three applications that suffer from this off the top of my head are Windows Media Player, Winamp and iTunes, when adding files to the library. I understand adding and removing files from the library has to be an atomic operation to prevent race conditions, but I should be able to play songs while the process runs in the background. You could argue that this is an application problem more than an OS problem, but I've seen plenty of OS operations use
modal dialog boxes when they were not necessary.
This isn't a problem only on Windows, because I've seen and suffered the same behavior on OSX and Linux.