Haven't seen much discussion of this, so here's a "vote":
Just upgraded a three-node Xsan to MOSXS 10.4.11 and Xsan 1.4.2; worked like a champ on all three: dual G4 (800MHz) desktop, dual G5 desktop and dual G5 Xserve. (FWIW: It's attached to four XSRs of widely-varying ages, via a QLogic SANbox 5200.)
The volume stayed online, as designed, the whole time, including four reboots - I missed the 10.4.10 update (required for Xsan 1.4.2) on one of the nodes, so had to install 10.4.11, reboot, then Xsan 1.4.2 and reboot on that one.
Apple changed the specs since the 1.4(.0) release (of Xsan) to exclude G4 desktops, so I'll probably replace it with another G5 desktop/Xserve at some point soon, though I don't see any need for urgency.