Saw one at Fort Lauderdale Executive in Jan this year.
I was taking a few shots of a lovely Grumman Mallard and was walking past an exec jet hangar, when in the back I noticed a Twotter. I saw a lady working in the hangar and asked if it was OK to take a shot of it and she said no problem. Next thing a bloke shouted 'No photo's of that aircraft! I said I'd asked and been authorised but he said you can shoot anything on the field apart from that one!
It was in very basic US colours and displayed the serial in a most odd way. It was something like 82-23-835 and was riddled with antenna!
Lovely aircraft
Regards
Reggie AKA The Cameraman