Improve QA.
There are so many glitches, it is pretty embarrassing as a product. Management truly chose to roll this out before it was ready. Problem is, it is not a paid service, but is an add on service to an already existing product. If people had to pay for it on it's own, there is no way they would have rolled out in the condition it did. No one would have bought it.
1) Get rid of "ghost" Fastpasses.
2) SPEED! Especially with foreign visitors who are spoiled by internet 4 times the average in the US, this product is clunky! (They have fixed this significantly, so props to them. I used to not even be able to log on before I was bored, but it must stand up to the pressure of Holiday crowds on their wifi system).
3) Make sure that there are NO glitches around purchases. People will roll their eyes if they can't get into a Fastpass line. Make them feel like their financial security is at stake, and you are looking at a class action lawsuit. Think Target. If a guy can do it there, Disney can't pretend it won't happen in the parks.
4) Why in the world are there glitches with it not opening up the rooms? If this is an error on the part of the front desk, they need more training. If this is a coding error, it should be permanently fixed... FAST. Again, a security issue. This should be as iron clad as the purchasing feature.
5) Yeah, I'm sad to see my days of 4 plus fastpasses are gone and not being able to have fastpasses for the major rides, but I will hold judgement. If it's truly a day where not EVERYONE in the park can physically ride a single ride because of capacity constraints (Mine Train), I understand.
In short, make what you have WORK-- FAST. Otherwise I'm not going to waste a "vacation" QAing your product for you again. You should pay me to do that, or at least provide enough perks to make it worth my vacation time. The CMs in the park are often failing at this (having bad or indifferent attitudes), as they are the ones who have to face the wrath of guests dealing with glitches. Frustrated guests are NOT returning customers.
If the product is so bad that the front line doesn't care if guests are having a good experience at Disney World, then this is a serious issue internally for Disney. Honestly, the new Cars Land and Fantasyland are what is carrying Disney Parks and attracting the increase in customers, not MyMagic+. They have about 1 year, MAYBE 2 after Mine Train opens to get their act together, or the revenue stream will be seriously affected.
Once it is working, there are a lot of tweaks that would make the experience more magical. Fastpass incentives to improve crowd flow and take pressure off some of the major rides. The interactive queues sound fun. Customizable magic band (not the covers or bling, but some of the leaked examples where it is printed on the band itself so it's less bulky). Once off site guests can pre-book attractions, allowing more flexibility to change Fastpasses same day, such as allowing multiple tier 1 rides or riding the same ride twice. That way everyone gets a fair chance at reserving the major rides prior to park opening to fit their vacation style, but if there are spots left over, they make someone's day instead of going unused (I am assuming that off-site guests getting pre-booking is a goal- otherwise the whole idea that it will make visitors more committed to going to the theme parks is rather silly. Onsite guests are already pretty committed to going to Disney. It's the off-site guests who may try to defect over to US or Sea World that you need to commit with prior plans).