My Rose has an Alfine 11.
Turbo setting on the Bosch motor is '200 per cent' rather than '250 per cent' to take account of the hub.
I've still had one break, lost second gear which I understand is quite common whether the hub is on an ebike or not.
To be fair to Madison/Shimano, they replaced the hub even though it was well outside the warranty period.
As Phill says, it seems to need very fine adjustment to avoid missed gears, particularly higher up the range.
When it's in adjustment, I think it's great to use and I wouldn't want scabby derailleurs.
But it's always at the back of my mind that a missed gear is only a change away which rather takes the shine off using it.
Kalkhoff fit an Alfine 11 to an S-pedelec, which could well be the worst of both worlds - if the motor doesn't conk out, the hub will.