One of the things with a large framework is that moving to a completely new direction is more challenging than it looks. So, at times, ember has made unrealistic promises — and Yehuda alluded to this in the keynote — but one can learn from it and get better.

As for Fastboot, it has its edges but there are people using it in production (DockYard is one, if I'm not wrong). ember-engines also says it's experimental and it does have some missing stuff (from my experience) but what is there works well.

Some of the things perhaps needed a rewrite of the underlying architecture. One great thing about ember (apart from v 1.13) has been just how painless it has been to upgrade. All the major changes they have made have largely been drop-in. Getting to that kind of backward compatibility is also a pretty impressive feat considering how big it is.

So, all in all, I agree that some of the things were overhyped and unrealistic but it seems they have learned from it, and I think that's just fine.