Its been a long wait, however, as of today you can now get your hands on the latest update to the AppleScript Language Guide. The copy that Ive been using for the past 6 months is dated 1999. Yikes!
With the release of AppleScript 2.0 (accompanying Leopard) there is now support for Unicode, so you can do things like this:
The application object has updates as well, such that you can check whether an application is running, is it the front-most application, what version is running, etc. There are also additions to scripting support across the system, for instance, network preferences are now scriptable. You can find all the release notes for 2.0 here.
If you are new to AppleScript, there is an AppleScript Fundamentals section that offers a good high-level overview of AppleScript from Objects to Scripting Additions to Commands, among other topics. On that same line of thought, you may also want to spend some time poking around the debugging tips which includes an updated section on handling of errors with try statements and error statements.
You can download a PDF version of the file that is handy if youd like to print a copy.