As you may know: to run AppleScripts that were compiled on a PowerPC machine on Intel machines (and therefore Snow Leopard) requires Rosettaan optional install on your SL install disc. While Rosetta is a fairly small install, some people have expressed an interest in staying Rosetta-free. There are quite a few of these types of AppleScripts here on the site and I'm working on updating them to Universal Binary (although a good percentage of these in the Retro Scripts category probably won't be updated by virtue of being obsolete). Long-time visitors may also have some of these scripts in their collections.
While you could wait for me to update these kinds of scripts to UBdisclosure: one of these days I will get around to admitting that I am a notorious procrastinatoryou can update these scripts yourself by doing what I would do: open the script in AppleScript Editor, noting whether it is a compiled Script (.scpt) or an Application (.app), and re-save it. It will be re-compiled for your machine type, and if it is an Intel machine, will run without Rosetta. The "Run Only" and "Startup Screen" checkboxes can be left unchecked. Script Applications that use idle handlers need to be checked "Stay Open".
During the Save, if AppleScript Editor informs you that the "Document Format is Read Only: This script application is in a format that is no longer supported...", the case for non-bundled applications compiled pre-SL, just click the "Save As" button, and proceed with the save. In Snow Leopard, single-file-type apps are no longer supported. The defacto Application type is a bundle.
The AppleScript Release Note: 10.6 Changes page at Apple has more on this.
Macworld's Jason Snell has written up a great review of Snow Leopard. With Regard to the Rosetta installation I mentioned earlier he opines: "I can only assume that making Rosetta optional is an attempt by Apple to goad users to upgrade their apps and to shame developers who still haven’t recompiled their apps to run on Intel chips. But given that most everyday users have no idea which of their apps are Intel-native and which are PowerPC, this seems unnecessarily harsh."
I know I'm going to be repeating this a lot: as of Mac OS 10.6 the Script Editor application has been renamed AppleScript Editor and has been relocated from the /Applications/AppleScript/ to the /Applications/Utilities/ folder.
Also, Rosetta, which allows PowerPC-compiled applications and AppleScripts to run on Intel Macs, is an optional install. Most AppleScripts on this site are either Intel-compiled or Universal Binary, but some older scripts may not run without Rosetta (especially if you had downloaded older versions of them or those that I never got around to updating as Universal Binary). So when performing your installation of Snow Leopard it's probably a good idea to include Rosetta.