I bought 9 of them for a bike hire business. Mine had the original Impulse motor. I had motors replaced on 4 or 5 of them. I have now closed the business and sold most of my bikes.They are great bikes but I'm not sure I'd buy one now that there are a number of similar alternatives.
I currently like the Winora Radius, this uses the Yamaha motor. KTM and Reise&Muller also have similar bikes with Bosch motors.