OS X client doesn’t include useradd or groupadd utils, probably as small encouragement to spring for OS X Server. That means that if you do a colo with OS X client, you’re screwed if you need to add users. OSXUserUtils fixes that (use the -m flag to override a dir creation bug in this version).
You can run repair permissions from the command line, i.e. via cron job.
Show Desktop: The best thing about Windows, now available for the Mac (be sure to enable the menu bar option).
Lars Duening left a very detailed comment on the Drive Dock post, with his observations on the comparative user experience between Aqua and X11/KDE.