Long reply, and I am very sorry about it:
There is an article on theme park insider about FP+ and if the program can "scale" (will it work on a broad range). It's called "Can 'Magic' scale? That's Disney's billion-dollar question.) I can't link to it, but it's very interesting, especially since it mentions that the money from the people control system that Disney's implementing is sucking funds from Disney Hong Kong, Star Wars land, Resorts, park upgrades, monorails, infrastructure, etc. I found this article very interesting. Hopefully it hasn't been here before, but if so, please forgive me. Basically they are diverting these funds into a sinking system - a system that Disney did not need in the first place.
Besides, Disney's IT is pathetic at best - my brother works in IT, and he swears that IT is the backbone of every major corp. You live or die by your IT.
Our last vacation was the most stressful vacations I have ever had. I ended up yelling at my mom. I never yell at my mom. We ended up missing multiple FP's for several reasons (which we never have before):
Have a nice lunch (My LO loves Jake, and we had a very relaxed lunch at H&V)
Wake up a little later because of the LO
Go to nap at 12pm because of LO (no nap=super cranky toddler)
Go to bed at 8pm because of marathon and super-cranky LO
We missed 3 of my favorite rides that were usually non-fp because the standby lines were too long (Mansion and Pirates), and also felt rushed to get to rides (especially Peter!) because god forbid we miss that 1 hour window. Or, we had excessive downtime and we couldn't do anything because stopping was not an option. As any parent of a toddler knows - one must keep moving (stroller or otherwise) lest toddler have meltdown. They are like sharks that way.
MK was the worst. We had FP+ for Pan, and when we got there, the FP+ line was past the old legacy area. I freaked out. I've never seen the line that long! Fortunately, there were some very kind CMs who suggested that we ride the IASW (Also, a new FP+ line, again, never needed to be one in first place), and they all assured us that they would get us onto PP with minimum wait, no matter what.
One of my very good friends who works at Disney said that this FP+ was a side add-on thing. Basically, the
MDE and the MB were only meant to be a room key/charging combo. But then some person came along and thought that it would be great to add FP in, so that you wouldn't have to carry anything. So this system was never meant to handle FP+ - and that's the cause of a lot of the issues.
Anyway, sorry for the long post (hopefully it wasn't as long as the new FP lines are.

)