We just took delivery of our first M1000e and blades, it all looks realy good except for one thing which i thought i would raise so that people don't spend hours trying to solve like i did.
The CMC (the main chassis DRAC) acts as a layer 2 switch for the iDRAC's on each of the blades and the switches. This is where the problem resides, there is no facility to setup VLAN tags on the CMC or the switches/iDRACs. So if you want the dracs and the switches on different subnets you have a problem.
We actually managed to set the ip's on the powerconnect switches onto a different lan but we are stuck with the iDRACs and Brocade switches on the same subnet. I find this a bit of an oversight for what seems and otherwise well thought of product and its actually removed functionality which was in the normal DRACs
I confirmed that this is the correct operation form Dell support.