I personally like 2000 better then 2003. 2003 seems to be a little bit more restricted, but it does have some nice recovery features... remote desktop was revamped I believe to where it is useable... But if you are looking for huge obvious differences like from nt 4.0 to 2000 you won't find nearly as many.
Window 2003 server includes IIS server in it. That is the biggest advantage on top of better File System controls.