I just read this Switch User Profiles on Jelly Bean – xda-developers
and I gave it a shot on my Gnex that is running PA 1.9.2alpha JB ROM and a franco kernel and it worked =D. Just thought I'd spread the word.
I personally like it. Now I don't have to worry about my inept girlfriend playing with my phone. I had one crash switching profiles, but none since. I like it more than I thought I would have. Once this is fully built in, having a admin profile to set permissions on the others is going to be really nice. Hiding apps from the drawer works for now though =P