It really wasn't a bad operating system. In fact it kind of blew its (lame) Win9X predecessors out of the water! I ran on Win2000 for years before finally switching to Linux. Of course Microsoft ended up going a different course with its newer "offerings" and I have nothing but pity for those who still have to use their products on a day-to-day basis.
I personally think the hypervisor architecture of 9x and its predecessors (starting at Windows/386) was far more interesting and innovative; while Win2k and the NT line are "traditional" OSes, 9x and 3.x are effectively VM hypervisors that have default hardware pass-through. DOS applications had dismal performance on NT, if they even ran at all.
Win9X wasn't Win2k's ancestor. Win2k was from the house of Windows NT. WinXP was the merger of the two lines.
Probably very few people switched from Windows 98 to Windows 2000. That wasn't considered an upgrade path. That was installing a different operating system.
Technically Windows ME existed, I guess.
> It really wasn't a bad operating system
It was a wonderful operating system. It provided consumer desktop essentials (Plug & Play, DirectX 7, ACPI power management, Windows Driver Model (WDM), and support for consumer I/O interfaces like USB and Firewire) alongside a modernized UI, all running atop the NT kernel. I was extremely lucky to receive a free copy of Windows 2000 Pro as a student, because I rode that horse for years.
Then Microsoft added a green start button and dark blue backgrounds and packaged Win2k for home users as Windows XP.