Mixed Architecture/Same OS

We need to upgrade the nodes in our cluster from RHEL5 to RHEL6. My hope had been to do that by a rebalance/update procedure. So take 2 nodes out, upgrade them to rhel6, bring them back in, then the next 2, etc,etc. That means my cluster will at times include RHEL5 and RHEL6 nodes simultaneously. The only documentation I saw about mixed architecture was around mixing windows and linux, etc.

Is anyone running same OS/different version mixed clusters like this? Am I going to destroy the cluster?