We have a brand new vSphere 5.5 environment and I knew right before going live Update 1 would be released. I generally don't jump on a major update release in production but considering the environment is not yet live, I am considering an exception. It may not be out long enough for much comment but, if anyone has good or bad experiences with this upgrade I'd appreciate any information.
Also include if you went from vCenter 5.5(b) to Update1. In my case it will be vCenter 5.5 to Update1