Alright, here's what may be a bit of a doosy.  In an effort to save costs on liscensing IBM has reccommended that my company take a websphere 6.1 cluster and upgrade the NDM to WAS 7 leaving the rest of the cluster wish WAS network deployment 6.1.  The reason we are considering this is because we need a websphere instance to manage our Data power boxes. 

The question I have is, while I know this CAN be done should it?  I know websphere 7 uses Java 6 and Websphere 6 uses Java 5.  Could this potentially cause any issues?  The NDM itself does not run any applications locally, the nodes are on different physical servers so i dont believe this would cause any issues on the application side that I have been able to find.

Any idea's/information would be greatly appreciated!

I currently have a mixed version cluster running in my environment.  I have a deployment manager running and two sepperate physcial nodes running WAS ND 7.0.0.9 and a single WAS 6.1.0.29 node.  Thus far, I've not experienced any issues with this setup.  I also have another 6.1 cluster managing all 6.1 nodes.

Pertaing to whether or not you should upgrade your Deployment Manager in place...  I opted not to upgrade my deployment manager. Instead, I stood up a new deployment manager on the same hardware where I am running the WAS 6.1 DMgr.  The new WAS 7.0 ND DMgr was obviously installed as a new binary install.

Keep in mind that the licenses you own for ND are for the physcial resources.  You can run multiple binaries on the same hardware...

Ultimately, my descision not to upgrade my DMgr was simply that you don't get all of the benefits of WAS 7 when upgrading from WAS 6 or another version.  Specifically, it pulls the old issues that were part of WAS 6 up into WAS 7 like the security and certificate issues.  Also, why introduce a potential risk by upgrading?  Deploying in parallel gives you an upgrade path if you want to federate your 6.1 nodes into 7 later, too, as example.

Hopefully this helps you out.

Erik