The main issues you will experience arrise from the new Windows Firewall being turned on by default after the upgrade to SP2. It blocks all inbound traffic to the workstations by default. If you do not make modifications you will not be able to remotely manage the workstations, connect to them using VNC or Remote Desktop and if your AV server will not be able to monitor workstations.
The good news is that you can use Group Policy to setup all of the Firewall settings before SP2 is rolled out. The first time they boot up with SP2 they will have the firewall settings that you need.
You need SP2 on an administrative workstation before the new Firewall group policy settings will show up. Modify Group Policy from this workstation. Firewall settings in Group Policy are in Computer Configuration => Administrative Templates => Network => Network Connections => Windows Firewall. There are two sub-folders. One is firewall settings for computers logged into the domain. You will want this to be more lenient to allow fior management of your workstations. The Standard configuration is the Firewall configuration used by the computer when not connected to the domain. You will make this much more restrictive for laptop users when they are out of the office.
If you have any specific questions about configuring the firewall feel free to email me.
Here is a link to "Deploying Windows Firewall Settings for MS Windows XP SP2":
http://download.microsoft.com/download/6/8/a/68a81446-cd73-4a61-8665-8a67781ac4e8/WF_XPSP2.doc