A friends business uses 2 * G5 on OS10.2.1 (I think) to access an SME5.6 fully patched server with no probs to speak of, tho the first cut of OS10 was a pig and he ended up using a different network stack for a while.
OS10 is a huge improvement as long as you use a later cut; if using Dreamweaver spring for Gigabit NIC's & switch, the difference is amazing.
Make sure the users are memeber of the group that has the correct access to the ibays - you will want/need to nominate the network share rather than browse to it (in OS9/OS10??).
HTH