i'm going to second (third? fourth?) tabs in the finder windows with springloading.
also with tabs, i would love to see them be able to be rearranged a la
adium 2. be able to move them around in one window, drag them out to create new windows, and drag them from one window to another.
listing in the finder of your path just under the normal buttons a la
pathfinder
system lock down similar to XP Pro. in some settings, the administrator can allow CTRL+ALT+DEL to give a menu, by clicking "system lock" or hitting Enter, the system can be locked down with having just a small login window. no other user can log in other than the one who locked it.
switch user
without losing network connections or apps stopping their tasks because another user starts using the same app. mostly the network connection bothers me the most. in the first few developer seeds of 10.3 the network connections were not disabled when using fast user switching... it was nice.
allow apps to not show up in the dock if the user does not want them to, but leave the apps menubar functioning.