With OS 9, Apple finally brings multiple users and groups to the Mac. All users get their own preferences, choices and access rights. Normal users have unlimited access to applications and the other two get limited access. An improvement to the Choosers feature for opening file servers now allows it to open all volumes and resources selected, not just the one highlighted. Notification dialogues are now handled by the Notification Manager.
Dialogue boxes are modeless, popping up without stopping other processes.
System performance felt slower, partly due to the increased OS memory footprint going from a tuned 15 megabytes to more than 22 megabytes. Turning off unnecessary or unwanted extensions and control panels decreased that by only 1.2 megabytes. A second, clean install seemed to partially clear up this problem, however. This makes the application abhorrent to use if you detest this kind of thing. Otherwise there is no compelling reason for post-OS 8.1 users to bother.