It's quite weird to speculate how some of the most ardent proponents of the Mac who are no longer with us today would react to Mac OS X.
Don Crabb was a jovial guy who liked the classic Mac OS but wouldn't hesitate to point out where Apple went wrong. I think that he'd be throwing a lot of rocks at Apple's beta to make sure that they get things right for the release, but by the time of the release I think he'd be plenty happy.
More than just Mac OS X, I have to wonder how he'd have reacted to Apple's darkest "beleagured" days, the return of Steve Jobs, the Microsoft deal, and the re-emergence of Apple as a power to be reckoned with.
This is one guy that I truly wish that I'd met when he was still around.
As a programmer, tinkerer, and smart-mouth geek, I think he would have loved Mac OS X. It's silly to say that I wish he were alive to see it today, since I just wish he were alive period.