Oh c'mon, if the Mac userbase has doubled over night without us realising [did it?] it's still miniscule compared with windows. Or are you counting ipod sales?

The fact it's now based on unix [and soon intel processors] just compounds what everyone with a PC, who commented, said all along about Macs doesn't it? If the future of Mac is running unix on a PC in a pretty shiny plastic case for 1.5x-3x the price, let's hope he makes money from iTunes and Pixar

As for root accounts and where XP comes from - afaict my windows XP install has an administrator account and separate user accounts and afaict the NT 3.51 / NT 4 / Windows 2000 base that it comes from is different from the dos-based Windows 3.1/95/98 et al.
afaict, it prompts for the password [run as...] and it doesn't allow significant changes to the system under normal user accounts. [But since your normal user account might have your CC number and various other sensitive data that's fairly moot if you run applications that access an untrusted network] Good point though - does the Mac have applications yet? I guess it has all the ones that would run on linux ...oh and photoshop

OTOH, I'll concede that it's not trivial to ensure that the security protection on the file system / registry et al are good nor that there aren't applications that don't have problems if you go too far. But then, your average user isn't likely to be a unix-security expert either.
Afaict, there are rootkits written for unix based systems as well as viruses et al for windows systems and security bugs are found [and exploited] in them all - in applications, in the OS, in macs and pcs.
There's no magic OS or browser to install that removes security as an issue.