Mark,
I've been flying with the UAT Skyguard for about 6-MO now in the Texas, Louisiana, Arkansas area and I've yet to have any air traffic controller ask me ANY question about my ADSB capability. Even if I leave the Skyguard squawking 1200 and I'm on flight following with a squawk entered into my regular transponder, they've never asked me about the ADSB squawk. If I forget to change the squawk on the Skyguard, but have switched back to 1200 on my regular transponder, I've still never been asked about it. My guess is that the large majority of our controllers either don't yet have the proper equipment, or they're completely disregarding the information at this early stage of ADSB. That said, having traffic displayed on the iFly 720 is invaluable to my flight operations here in congested Dallas, TX. Once you have it,,, you won't be able to fly again without it. It really does add a substantial amount of peace of mind. The weather information is a huge plus,, but for me,,,, traffic information is the biggest advantage.
Best,
Chad
Plano, TX