Screenshots at the end of the post!
I was recently given the opportunity to try out Mac OS X 10.6 Snow Leopard build 10A96. I got some screenshots (see the end of this post), and here's what I noticed about my experience:
it really seemed a lot faster. With the battery at 98%, there were 5 hours 11 minutes left! Some screenshots were taken of the setup assistant and now instead of the little "Welcome" movie playing at first boot full screen, it runs in a window.
Looking at System Preferences, the Desktop & Screen Saver pane was redesigned, and screen savers only work under 32-bit (or sysprefs can only set the screen saver under 32-bit mode). There is nothing really especially new in the system preferences, except a lot of things only work in 32-bit mode. And as I checked out the Apple menu with System Preferences running, you can force quit the specific app if you're holding down shift (this is probably in other OS X versions, though).
The Finder was really interesting: now in the path bar you can change folder sizes on the fly, without having to press command+j for the options. It's also interesting to note that windows' close, minimize, and zoom buttons have higher contrast/brightness (I'm not really sure of the terms). Also, menu selections are a brighter blue.
Also noticed was a new font panel and options for Spaces allocation in the Dock. Not only that, but the login screen is by default blue instead of the Aurora wallpaper. QuickTime is still version 7.6, not yet QuickTime X. Preview's PDF sidebar is redesigned and looks cleaner by using smaller font.
The most annoying bugs I found are that dragging a file into a folder doesn't cause the folder to change into the open folder icon, indicating it's ready to accept the file, but accepts the files anyway. Also, you can't drag a file from a stack into the trash anymore.