I'm pleased I found this thread, because I was about to post my own.
When UI5 was released, I had nothing but problems with trying to upgrade my Vera 2. I'm starting from scratch in a new home now, and hearing that UI5 is stable & people are running it on their 2's is good to know. I'm mainly interested in getting DM to work, because I couldn't get it going on UI4.
EDIT: I just upgraded remotely. Admittedly, I removed most of the devices & scenes from it while I'm in an apartment, but the upgrade seems to have worked well!