http://docs.info.apple.com/article.html?artnum=301984
Just confirmed it… doesn’t lock up the CPU anymore. Coooool.
Appears to have fixed the ‘pause’ action in Automator as well.
On my dual 1.8gHz G5 Script Editor takes 1.5% during delay, and Automator takes 3.1% during pause. This is especially good news for Automator, which used to take up 90%+ regardless of how the workflow was saved and executed.
I wanted to mention this, but I hadn’t tried any of it out. (Personally, I’m more interested in “do shell script”). Thanks for the info silvermeteors. 
Thanks for this info. Does anyone know about the “performance” issues with do shell script? In my experience, there is a huge performance hit when calling a shell script and from what I can tell this hasn’t really changed with the 10.4.3 update.
The shell scripts themselves don’t run slowly, but calling them takes a long time. In my app, for example, I had shell scripts in a number of AppleScript handlers and I was calling passing a piece of data along from one handler to the next. This took a long time and I couldn’t figure out why. But now I have combined all my shell scripts and just pipe the data through. This is much quicker, although it does lead to a lot of redundant code. So exactly what performance issues have been solved?
http://www.satimage.fr/software/test_05_08/speed_test_result.html
Edit:
http://lists.apple.com/archives/applescript-users/2005/Nov/msg00172.html
“The improvement is in fact very real, but it’s not the one you were looking for. This particular bug had to do with repeated calls to “do shell script … with administrator privileges”: successive calls would be delayed by a few additional seconds each time.”–Chris Nebel (AppleScript and Automator Engineering)