My PeeCee and Powerbook sit side by side on my desk. I never got around to using the Mac pre-OS X. It just didn't have any attraction in my IT environments. Two days spent with OS X, however, and my Mac is now an indispensible part of my wide array of tools for attacking problems in a highly complex computing environment.
We have AIX, Solaris, OS/400, NT, embedded DOS, WinCE and Linux all chugging away 24/7 doing those things that are most appropriate for them to do. We do a good bit of distributed processing using a variety of tools and languages.
I could never do without my PeeCee and NT/2000. There are just too many of them in business spaces and I need the money they pay me to program them. And the PeeCee has a wider variety of cheap software to interact with the Big Iron.
But for the many things where my PeeCee is fussy and closed, the BSD underpinnings of my Mac compensate. The Mac, in short, plays nicer with the other kids in the sandbox than does NT/2000.
If you're a serious computerist, i.e., your groceries depend on it, you understand that there is a convergence coming. OS X is a preview of that convergence, as is Linux. We'll be back around to the day where the best product wins instead of the best marketeer.