I apologize for missing some SheepShavers malfunctions. I use it for a special drawing application I purchased years ago and it works perfectly well for that purpose, very stable and fast. The current vendor of the software asks half a Kilobuck for an OS X version of the software that combines any bug of the old version with a few cosmetic adaptions. So I keep at using the old version. The only annoyance for me is that SheepShaver does not support recent trackpads well (at least using Lion). But with an iMate adapter you could just use an old ADB mouse and a Wacom pad, which also provides a perfect classic tactile feedback.

Recommendation for PPC users that are interested in using old software on recent hardware: Visit the Macintosh Emulation site (E-Maculation). Undergo the inconvenience to install SheepShaver and check if it might be a solution in your case. Note the existence of SheepShaver Wrapper and installation instructions ;-) A usable ROM file can be obtained from a System install CD. Be aware of the fact that even experienced comrades encounter difficulties and that SheepShaver has some bugs, so it might turn out not to meet your needs.

After I made it to the point of running SheepShaver it was quite easy to replace the default Mac OS installation by my preferred setup. I just copied my preconfigured System Folder into a place where it is accessible for SheepShaver at startup and selected the Mac OS implementation with the Startup Drive control panel (the late version lets you pick one of several System Folders on the same volume).