XP is NT5.1
It's still the same crap code of NT!
I'm not sure how you get to "It's stil the same..." after pointing out that they're newer versions. The reason they have new names (version numbers, or whatever) is because they are not the same.
FWIW -- I am an MCSE and Windows developer with twenty years of computer experience, not all of it with a Microsoft O/S -- I have been extremely happy with Windows 2000. It was a major improvement over NT 4.0. We had very few problems with NT here in the first place (15 servers, 150 clients), but the upgrade to Windows 2000 has made problems almost nonexistant. Any issues we have run across have been because of Dell hardware, not because of Windows.
While I would say that Windows reliability is still not quite on par with xNIX O/Ses, it's honestly not that far off anymore.
I use both XP and 2000 at home and have had the same experience there. Very stable and reliable. Any problems trace back to hardware.
Win2k Advanced Server was a major jump. Great OS, IMO.
My credentials are similar to yours and my experience is the same. XP and 2000 are very stable and reliable. I can tolerate Linux with 25 years of UNIX background. It's not a good fit for the unwashed consumer. It is perfectly fine as a server OS for web servers and databases. I also use it for some embedded systems when I'm not deploying on QNX.