The only bad things I remember about Windows 2000 are that some software written for Windows 3.x and 9x had compatibility issues and it took an eternity to boot up. It was go take a coffee break as soon as you turn your computer on for the day bad.
It's a tradeoff. A Win2K system was pretty responsive when you log in after a reboot/startup, but you've got to wait for that experience. In the days of spinning disks and single core CPUs, you had to fight those still-starting services for resources, making the first several minutes of XP usage painful.