There is no free lunch with the FAA and ADS-B is a case in point. ADS-B out is the ultimate in big brother (aside from your cell phone).
Yes, with the new transponders, if you have both out and in, you will be able to see traffic. With just out, you can see traffic on your IPad with ForeFlight and other setups. The carrot the FAA has put out there is free weather—good but not near as good as subscription XM.
The catch is that you are tracked by N number anytime you have your ADS-B turned on regardless of whether you are IFR, VFR (on a flight plan or not), and any other flight you might perform.
Is this a problem? Look at it this way—you are flying on a crystal clear day and you clip the corner of a restricted area with your ADS-B turned on. Busted! Currently, there is no protection against the FAA coming against anyone who has their ADS-B turned on and clips any airspace. Look out GA pilots.
There is an office in Atlanta which stores data on every ADS-B equipped aircraft for every flight, every day, and forever.
I may have to buy an ADS-B out transponder but that does not mean I have to turn it on. I have flown over 30 years without in cockpit traffic avoidance except my eyes and I plan to keep it that way. Besides, drones will probably not be required to have ADS-B and there have already been mid-airs (government denial or not).
General aviation flight, the last area of true unsupervised freedom, is about to lose that freedom.