Despite Apple's suggestion on the Snow Leopard specs page that, when going from Tiger 10.4.x to Snow Leopard, you should buy the box set...
Upgrading from Mac OS X v10.4 Tiger: If your Intel-based Mac is running Mac OS X v10.4 Tiger, purchase the Mac Box Set, which is a single, affordable package that includes Mac OS X v10.6 Snow Leopard.
...I bought the family-pack DVD, and installed it on my 10.5 laptop and my 10.4 desktop without any problems.
[robg adds: Jason Snell covered this interesting fact in his Snow Leopard review, where he pointed out a key benefit of Apple's honor system approach:
...the standard version of Snow Leopard is a bootable "full install" disc that doesn't actually check for the presence of Leopard in order to install. This also means that if, at a later time, you want to wipe your hard drive and reinstall Snow Leopard, you won't have to first install Leopard and then run a separate Snow Leopard upgrade on top of it. (That sound you hear is a thousand IT managers sighing with relief.)
There are advantages to the box set, in addition to complying with Apple's licensing terms -- you get new versions of iLife ($79) and iWork ($79), which essentially lowers the cost of Snow Leopard to $11.]
I've been wanting Apple to add the ability to close an app or window through Exposé since I first saw Exposé. With Snow Leopard, they've at least gone part way there.
If you invoke Exposé's All Windows or App Windows mode by whatever method, you can then click on a running app in the Dock to have Exposé focus on that app (either changing focus from one app to another in App Windows mode, or switching to App Windows mode from All Windows mode).
This is nice, but better yet is that the abbreviated Dock contextual menu will show, on a single left click, allowing you to quit, hide, or set options for the focused app. The only thing missing now, IMHO, is the ability to close a specific window from Exposé, but I guess we can't have everything (yet)!
[robg adds: This only works if you click on a non-active app in the Dock while in Exposé's App Windows mode. I first tried it by clicking on the currently-displayed app's Dock icon, but that simply exits Exposé. Click on a non-active app, though, and it works as described.]
You can reveal the location of a recently-used item by holding down the Command key while looking at the Apple menu's Recent Items menu. With the Command key held down, the wording of the menu items (for Applications and Documents) changes from someitem to Show "someitem" in Finder.
[robg adds: This doesn't work in 10.5, at least not that I could figure out.]
I have been using the Screen Sharing application bundled with Mac OS X (it's in (/System/Library/CoreServices) to do all my VNC screen sharing with Windows PCs.
Since I upgraded to 10.6, every time I try to connect to a Windows PC, I just get a white screen after the password login screen.
I solved this by selecting the Screen Sharing application in the Finder, pressing Command-I, and clicking on the 'Run in 32-bit mode' checkbox. This solved all my problems; Screen Sharing now connects on the first try every time.
For those of you familiar with the old AppleScript Studio in Xcode, you may find the following information handy to know for Snow Leopard. Apple has changed quite a lot about the way things work, and you have some reading to do to get caught up.
One of the most important pieces of information from the preceding link is the part at the top of the page that reads:
AppleScriptObjC obsoletes AppleScript Studio, which is deprecated as of Mac OS X v10.6. Developers using AppleScript Studio should migrate to AppleScriptObjC, and should start new projects using AppleScriptObjC exclusively. AppleScript Studio development is still supported, but functions for creating new projects have been removed, and the AppleScript Studio palette in Interface Builder has been hidden. To re-enable it, use this command in Terminal, and then re-launch Interface Builder:
As we've all found, you have to turn on Text Substitutions in every app that you want to use them in. This is reminiscent of needing to do the same when Spell Checking was introduced in Cocoa. Well, to enable both by default, just paste these three lines in Terminal:
After updating to Snow Leopard, I've been having issues with accidental input on my trackpad. I had forgotten where the checkbox was to disable the trackpad when I had a mouse hooked up, so I popped into the Snow Leopard help system to find the solution.
Unfortunately, there wasn't an answer there; the only thing I found discussed the "accidental input" option:
To make your trackpad inactive:
Choose Apple menu > System Preferences, and then click Trackpad.
Open Trackpad preferences. Select the "Ignore accidental trackpad input" checkbox to make the computer ignore the trackpad while you type.
After some digging, I discovered that the checkbox has moved to the Universal Access System Preferences panel, under the Keyboard and Mouse tab. Now if I could only find out why it was moved there.
[robg adds: On a related note, it appears the references "Ignore accidental trackpad input" checkbox is gone altogether.]