Windows 2000 Pro VS. Windows XP Pro

Our company is considering moving from Windows 2000 to Windows XP Pro but are trying to put together some facts like:
1. Advantages of XP VS. 2000.
2. ROI Information.
3. Compatability issues in a networking environment with XP.
4. Benefits of XP VS. Windows 2000.
Just a little FYI. No this is not for a school project I am looking for answers that come from experience with Windows XP that we don’t have that’s all. Any help would be appreciated.