I have to reboot a file server (with Home drives) but I have many users with gigantic network residing psts connected and I don't want to affect them. I'm not totally convinced anything will happen to corrupt the psts but I want to be careful. I could just send out a notice and have everyone reboot their pcs. That could work and I could just reboot everyone myself but I'd like to avoid that... Anyone have any experience with this... I'm feeling a little paranoid about this file server lately since I've discovered a slew of 10GB+ psts in use.

Rebooting causes a service outage. If the machine stores volumes, they are all inaccessible until the reboot completes and the File Server reattaches them. If the machine is a database server machine, information from the databases can become unavailable during the reelection of the synchronization site for each database server process; the VL Server outage generally has the greatest impact, because the Cache Manager must be able to access the VLDB to fetch AFS data.
All connected machines should be properly shut down to prevent any file system corruption.