So yeah the MineZ au server scared me a bit with a random message about hacked clients, but I'm pretty sure they don't know if you got a simple waypoints or radar set up. Pretty useful... I still got murdered by a player though.
I wonder if you could trick REI's minimap into loading the same waypoints for different MineZ servers?
One more thing: x-ray is pointless on MineZ and for me it only reveals lava and a few odd items underground, not ores, and screws up water after it's turned off. I haven't been using it.