From GA perspective, though, I just worry about the lag before it is widely implemented, because there will always be a bunch of non-retrofitted planes tooling around Class Echo without the proper transponder, so I just fear that relying too much on assumption that people are using ADS-B is worrisome, and people will have increased tendency to be "head down" instead of scanning.
I know other people have different fears, but this is my greatest safety worry in aviation for me personally. Lots of old planes even without strobes or Mode C in my area of country, Sunday fliers that do things that are sometimes not really advised.