Regarding the vibration issues, this is not present to the same degree on all of these Royal Enfield bikes. Some exhibit this more than others.
It has been my finding on the Iron Barrel bikes, which had a terrible reputation for vibrating, that they can be made smooth as silk with a proper crankshaft truing job. I would surmise that this is also the case with these new UCE bikes.
So, I would say that vibration problems are not necessarily a "fatal flaw", because they can be corrected. It might be a fairly big task to get the engine out and stripped down and corrected, but it can be corrected if you want it.
These pressed-up cranks are completely at the mercy of the person who is truing them before they go into the crankcase. If he doesn't true it down to a small run-out, then it vibrates.
You would not even believe how smooth our Fireballs are, after we really work at truing those cranks down to less than one-thou run-out. This is a miraculous improvement from the way they were as stock. And the less it vibrates, the less it's going to reduce the life of the engine bearings and other parts.
The UCE uses a crank that is VERY similar to the Iron Barrel, and it might even be the same crank that is used on the AVL. The truing of these cranks means EVERYTHING to the vibration levels you are experiencing.
In a production line environment, it is impossible to spend the time necessary to get perfect run-out on every one of these cranks as the bikes go down the line. Some get done better than others, and thus we see varying degrees of vibration issues in these bikes.