[When attempting to eject an external disk,] improved dialogs tell you which applications are using the drive so you know what to close in order to safely disconnect your drive.
Wow—you mean we have the technology for that now? Outstanding.
Now, without the sarcasm, I can't believe this qualifies for front page news on Snow Leopard. Mac OS X's error dialogs are regularly woeful, and this kind of sloppy user interface design (telling the user that something is preventing a disk from being removed, but not telling them what) should have been corrected years ago. It's neither an "enhancement", nor a "refinement", it's an "embarrassingly basic user interface deficiency that should have been fixed by now".