My experience is much like Greenergrad's, using ASR with properly prepared disk images to restore HDs on anything from LC 575s to iMac DV SEs in classroom and lab environments.

I recently attempted to create a restore image for a single partition install of OS 9.1 and OS X and was unsuccessful. The entire process, done is OS 9 because of using Disk Copy, seemed to go normally. After restoring, the machine booted into 9.1 just fine. The problem came when I tried to boot into OS X and it came up in a screwed up command line. (I'm a UNIX newbie, but know how to exit and reboot in command line-- no luck.) Restarts didn't help and I couldn't boot back into 9.1, so I restored it back to 9.0.4.

I understand that there is a version of ASR for OS X that Apple is working with now, but it's not currently available on Apple's Developer FTP site. I'd bet that when consumer machines start shipping with OS X installed that the new version of ASR will be a part of any restore CD that they come with, and that a new SDK will be available for download from Apple.

For a brief tutorial on the ASR process for OS 9.1 and earlier, check out my website:
http://tech.asd.k12.ak.us/tim/Resources/Tutorials/ASR_Tutorial.pdf