I've looked over posts and can't really find a definitive answer other than if you don't enter it you better hope the machines never turn off.
I've set up my ESXI 5 server and am only using the VSphere Client to access it. It has 16 GB of RAM, an iSCSI connection (soon to go from XO cable to actual fcals), 5 VMs including the Power Panel appliance. It's currently running in evaluation mode, and I have a free license code. I'm not sure exactly what will happen when I enter that code. I know I'm going to have to at some point, and once this takes over as my main box (migrated from VM Server 2 on Windows 2003 x64 server) it needs to run 24/7/365.
So - when I enter this code what will happen to my machine?