I just received the new CUI on both my HWS's. I have to admit after reading these forums I was pretty apprehensive but now that I have them I haven't noticed any major or deal breaking issues.
The system is a little slower but not enough to matter to me or the wife, we actually prefer the new guide to the old one.
I received "CUI my gift" on Father's Day

, I had worked that day and after getting home. I saw my wife was navigating around the update. I had told her that changes were a comin'. I didn't have a chance to soften the blow.
Other than turning off the PTAT, had a few shows to delete

. The TV didn't blowup or I haven't thrown anything at it yet. Sure there are a few things I'm not wacky about ,fast forward speed is one that comes to mind. I was worried about the possible slow down, the 2 HWS seemed to not suffered. The 2 Joey 1.0 don't really use those (kids) , my son says little lag but not noticeably slower than before.
My wife did comment about the caller ID font size(not a big deal)....I don't use it. The one thing I haven't figured out was retention of search items, sometimes I have 5-10 movies i search to see if they are coming on (i.e. Sleuth 1972) and I didn't have to type title in again ??
Overall experience has been fine.
Steve