PGY-1 -- Please feel free to take my perspective with a grain of salt. I thought I might uniquely contribute because my mentor worked on the inpatient psych unit at a large hospital, and was actually in the process of converting to 7 on/off from working weekdays with coverage by another attending that wanted the extra cash. Now the floor has two psychiatrists, and they alternate the 7 on/off.
With a family this work schedule is less compatible as noted above. IMHO, with families that have children not yet in school or another parent working, you would run into awkward day-care arrangements and have a harder time finding balance both in and outside of work with this schedule. As such, this wouldn't personally be a great fit for me as I see it now. This was one major deterrent for me when I was interested in EM.
Upsides for someone who wants the alone time? Sure, if you have time-consuming hobbies or a desire to solo-travel frequently. I think you'd need something of substance to make losing 1/2 of your weekends worth it.
My mentor is a very seasoned psychiatrist and has handled this change in style with ease. FWIW, I believe they "squeeze" in nearly an entire outpatient practice with their week off. You can do that sort of thing when the kids are grown, and you love your job too much to do much else! I think if they had a the perfect situation however, they would prefer it another way.
Cheers!