So I was very skeptical of the MM Share scenario but figured I'd give it a go. It was just my husband and I, and our share only cost $35 with number of families we had. So basically, if I got three pictures out of it, I broke even for what I would have paid if I bought them a la carte.
It was an absolute hoot! Even my very non-Disney husband had a fun time taking pictures. It was also a lovely relief to not worry about constantly asking someone else to take our picture (since there were just two of us). The magic shots were also something that we enjoyed.... and I say that as one who thought they were super silly before actually doing them myself.
Anyway, we had no problems setting up the share (even though we were a bunch of first timers). We had a minor hiccup when it came to downloading. It was unclear whether or one person was downloading for everyone or whether we were all responsible for downloading our own. We had a couple people almost miss out on their pictures because of this, but luckily one of the members of our share still had the entire batch downloaded and was able to get them to them. So, lesson there is just make sure everyone knows what they are supposed to do after taking the pictures.
If you have any other questions, I'm happy to answer them!