As I understand it, two aircraft equipped with both ADS-B out and in will communicate directly for traffic avoidance, without the need for ground stations and radar. If so, there will be a significant benefit for backcountry flyers. Up to now, ADS-B hasn't helped as much, and in the lower US backcountry not at all, because relatively few aircraft have ADS-B out, so that even fully equipped aircraft must be in range of an ADS-B ground station and the traffic has to be in range of radar to see it. ADS-B-in only equipped aircraft are "piggybacking" on other ADS-B-out aircraft.
So, if you have ADS-B out, it will be a benefit to leave it transmitting, even in anonymous mode, for direct traffic communication. The last two uncomfortable traffic encounters I've had have both been in mountainous terrain at 3000+ AGL. In one case, we were head-on and talking, and still couldn't see each other (I installed a pulse LED landing light after that one); in the other, I was overtaken by a Cirrus that went zooming by.
The ground-based weather is a crock, though; it would have been more effective to pay Sirius to provide it via satellite.