We have been using RHEV in our production environment since 3.0 and have I to say that the product continues to evolve with each release. The current version is very stable and offers all of the features we require from a virtualisation infrastructure platform. I am especially impressed with the self provision user portal and the performance of Spice as a remote desktop protocol, although it would be nice to have better client end support (OSX, IOS etc).
One of the biggest lacking features is the ability to replicate virtual machine configurations to another RHEV environment for DR. Our development team addressed this by producing a python script which calls the REST API and replicates VM configuration allowing us to restore data into prebuilt VMs. www.quru.com/rvsr
Overall we are very happy with RHEV and have deployed a number of roll outs to our UK based clients. Looking forward to the next release.
Disclaimer: the company I work for is partners with several vendors including Red Hat