Windows 2000 is time consuming to convert if you use a wide variety of software applications that are non Microsoft applications. They do have a program that will identify applications that are not compatible which  saves A LOT of time. An issue that arose for me was if an application is not compatible, you are stuck with finding(and buying) something else or trying to get the manufacturer of the application to make necessary changes.

I did find Microsoft support team willing and able to help through the transition as well as helping with working with vendors to get changes made.

Another dis-advantage is that it takes longer to boot a pc with 2000 - of course this could be considered an advantage also because it is a perfect opportunity to go get my morning coffee!