I bought a derestricted d4s Vive edition through my company's cycle to work scheme. I had been about to buy (and had tested) a far more expensive Mii-rider £1500 bike but some reviews online said "just save money and get a d4S". I watched some reviews and decided it seemed to fit my needs.
Cycle to Work scheme slowed down the order process painfully, but it arrived Tuesday. Very easy to 'part assemble'; the free mudguards have no instructions but there was a tutorial on youtube so that was easy enough.
Road test - I have tried the bike on the same route on both de-restricted and restricted speed and have some useful speed data from GPS app (not bike speedo):
THROTTLE ONLY
De-restricted: 22.7mph max on straight flat well surfaced road (impressive at 6'2 and 110kg)
Restricted: 14.1mph on flat straight road (speedometer said 15mph and limiter kicked in - speedometers always overead)
It's a very comfortable bike. It's not light and it's not impossibly heavy: weight is fine for jumping on and off bus or train and a flight of stairs but I would't want to carry it further.
Shimano gears are accurate and a useful range for uphill/downhill
Folding mechanism is stiff but intuitive. It doesnt fold as flat as a Brompton but wil work well for buses and trains or beside desk.
Brakes (hydraulic on Vive edition) are SUPERB - great reliable stopping power.
Build quality is high - feels reassuringly solid - no rattles or instability.
Ride quality far better on the 20" inch wheels than on the Mii-rider 16". No suspension but comfy saddle absorbs jolts.
Highly recommended as the best value for money fast, folding ebike.