We used MaxPass last week and overall, it was great. However, we did have a couple of glitches.
Before we entered the park the first day, I pre-loaded all 4 of our tickets onto all 4 phones and linked them. I assigned each ticket to a specific person and put that person's name on the digital ticket and on the paper "tickets" that I printed from my printer. When I handed the CM at the turnstile the paper tickets, she scanned them in and took the photos without matching up the name on the ticket to the correct guest. I noticed this as soon as she asked us to sign our tickets, but she assured me it wouldn't matter as long as we all had adult tickets, which we did. So the names on the app didn't match the names on the tickets. I told her we wouldn't always be together and were getting MaxPass, but she said it was fine. I even stopped by City Hall and asked if it would cause a problem ... they also told me it wouldn't, explaining that the only time they look at the pictures is when you enter either park. They said we just needed to be sure we all had all the tickets on all of our phones or that we had the physical tickets with the correct name printed on it when we entered either park. Everyone agreed they never looked at the photos when redeeming FPs so it shouldn't matter.
The way we used MaxPass was that I got everyone's FPs from my phone. Then if we were together, I also redeemed all of them from my phone at once. But when we split up, everyone redeemed their own.
Well, everything went just fine until we had FPs for Space that turned into "any attraction" tickets when Space went down during our return time. DD17 and DH were together and used their "any attraction" tickets early. Then I pulled 2 Matterhorn FP from my phone for them to use while DD14 and I went to use our "anytime" FPs on Indy. When DD17 and DH got to Matterhorn, DD17 used her physical ticket for her FP instead of using the digital. But since her physical ticket was actually linked to my name on the app, she ended up using my "anytime" FP without knowing it since her physical ticket did not have a Matterhorn FP so the system automatically used the "anytime." (Had she used her phone, the Matterhorn FP would have come up.) When I tried to redeem our two remaining "anytime" FPs at Indy, only one was there! The CM told me I didn't have an "anytime" FP but I did have a Matterhorn FP.

Luckily she let me on, but it most definitely DID cause a problem not to have the names right on the app.
The other glitch was that for some reason, DD17 was unable to book FPs from her phone when we weren't together even though she had all 4 tickets on her phone and we all had MPs. She even took her phone to Guest Services and they tried without success. They told her they weren't sure why it wasn't working. She was able to text me to ask me to do it, and I booked them with no problem.
So the main moral of this story is -- don't let them mix up the names on your tickets, if you get MaxPass it DOES matter!!