I know I'm weighing in late on this topic, but here goes...
The sooner Apple's customer base moves to OS X, the better for those users and the company.
Mac lovers everywhere want Apple to succeed. The path that Apple has taken is a bold new direction. I say, its really time. OS X is a step forward. It is stable. It is modern. It has the potential meet and exceed our expectations of OS 9.
I just got my copy of OS X 10.2 and am installing it as I write. I was an early OS X adopter, and frankly the version released in March last year was a disaster that I never got working on my older machines. 10.1 fixed those issues in October, and I've been happy with OS X for the last year or so.
Is it perfect? No. Is it better than OS 9? Yes. I think Apple is going to kick tail with OS X, but not with a 20% installed base.
I understand that there are many of Apple's faithful who have custom applications and hardware running in OS 9.x and before. Maybe its about time to upgrade. I remember the switch to PowerPC back in the early 90's. That was painful too, but it was direction that Apple chose at the time. It was costly for me and millions of Mac loyalsts, but it was the only choice if we wanted continue to own and use Macs.
The mantra of the entire computer industry is change. The industry is based on the fact that new software makes your old hardware obsolete. The industry (not just Apple) wants you to buy new machines every year. That being said, Apple has done a pretty good job of making sure that Classic in OS X and standalone OS 9 still function. In my experience, Classic works well even on older machines. Eventually though, people will have to let go of their old systems and upgrade to OS X if they want to continue to support Apple.
Personally I can't imagine any other choice for my computing needs. Apple is IT.