I reckon it looks like damn good fun. And it opens up a whole new way to ride. For a purely utilitarian approach, DH tracks that can't be reached by car are suddenly a lot more accessable and you'll be able to get in several more runs in an afternoon.
Then factor in the new terrain that is open. This bike allows the gravity assisted fun of DH on almost any track, bar technical climbs. I'm sure we all know of a sweet section of XC or all mountain track that we would love to take a big bike through, if it wasn't such an effort to get there. Or such an impractical struggle to get up enough speed to make that section fun. A electric DH bike fixes that. I don't want a moto because they are a pig to handle on singletrack and plow over everything. This bike however weighs no more than my Stab and in all reality probably handles better.
I don't see what isn't to like about it. I doubt it is powerful enough to rip up track badly, especially if ridden in a considerate fashion. It isn't too heavy, which used to be the major problem. It isn't noisy. And most importantly, it gives me more options to ride.
