I bought a Pi model B for my daughter. Nothing but terrible unreliability. Booting problems as you state, power problems with the USB ports, random hangs and crashes and problems getting half of the devices recommended to work.
I kind of expected that for the money but the thing that really pissed me off was when I raised these issues constructively on their forum, I was met with nothing but vicious denial and had my post deleted and account closed within an hour. Possibly the worst bit was the insinuation that I was clearly an idiot and this was all my fault. I'm technically literate (I'm quite handy with anything from an oscilloscope to GDB) but I can't imagine this doing well in the hands of teachers I.e. one of the target markets.
She now uses an old ThinkPad X61 and finds it a million times more useful and with all the extra bits required on the Pi to get it to work, considerably better value for money.
Not impressed. When your policy is to silence critics the product should be distrusted.
As for the initial design brief to produce a useful educational computer, I think it fails entirely based on the sheer amount of friction between opening the box and writing your first program. I was brought up on a diet of BBC Micros and Acorn machines and despite the brand association, the Pi is nowhere near the mark. Her school even bought 20 Pis that are wheeled out for open evenings and otherwise never used as well in favour of bog standard PCs running python.