Hi Paul,
it seems that Bill hit the spot with the mac address problem. The reason why we would like to use the OOB management network is that we want to be able to configure every aspect of the switch including the Uplink ports, LACP, LAG and so on without risking to get disconnected from the switch. If we do that with the inband VLAN we are connected to the same Uplinks the we would like to configure.
Even if something goes wrong with a firmware update or if the configuration has some problems the connection with Management VLAN is still working most of the time. The management could not be "part of the problem" and this gives us a little more confidence, especially because we are doing support from a remote site and are not so quick on location.