I agree with your reservations about the Share Everything plan. When it was first released, I was very reluctant to switch over as my bill with 2 smartphones and 2 basic phones would increase slightly.
At the time, I was considering changing my plan to 4 smartphones which I have since done. If I were to stay on my old plan, my monthly bill would have increased by $60 by adding the 2 smartphones at $30 each for 2 data plans. If I were to switch to the Share Everything plan with the 4 smartphones, my bill would only have increased by $20 instead of the $60 it would have increased on the Share Everything plan, so I made the switch. As an added benefit, I also have use of the mobile hotspot when needed. I have been quite happy with the Share Everything plan.
Good luck and hope you are happy with the new plan.
I'm in the four line boat too, and it's also part of the complication.
One line is for my mother-in-law, but she no longer needs it as she is now in a nursing home. I had to keep it on my plan until 11/26 or pay the early term fee. With that phone still on my account, it messed up the price compare tool on the website, so I never could get a good idea of what I'd be paying. Chauncey worked it out and I should save a few bucks. He also setup something that will auto remove the MIL phone on 12/7 (the end of my billing cycle), which is why he suggested I wait until 12/8 to switch plans.
I'd been attracted to the Share plan in the recent past, but I was unsure how that would impact my expense reporting at EOM (I get reimbursed for cell phone expense). On the plus side, I use a medium amount of inet (via 4G), the wife almost none, but the kid in college gets every mile out of her 2GB each month. I'm not going to tell her we're on a shared plan, which should mean I won't have to worry about her going over 2GB.
Yes, she has wifi (University of Florida), and uses it. I think a lot of her bandwidth usage is from Pandora when she's not on campus, but, I won't pretend to understand what a 21 yr/old does these days. 