The environmental effects involved in recharging the batteries can of course be reduced. The small size of the battery pack on an e-bike, relative to the larger pack used in an electric car, makes them very good candidates for charging via solar power or other renewable energy resources. Sanyo capitalized on this benefit when it set up "solar parking lots", in which e-bike riders can charge their vehicles while parked under photovoltaic panels.
Above all, the Brompton is a lot of fun to ride in urban settings. Its powerful enough to breeze up hills with near zero effort, but feels nimble. As with any Brompton, you probably won't win a half-mile sprint on it, but thanks to the pedal assistance, you most certainly will get off to a flying start. The reason it stands above other electric bikes is that Brompton has worked out how to apply power assistance to your pedalling so it feels natural. It also doesn't feel so much like it's trying to fight you once you reach the maximum, 15mph assisted speed.
E-bikes mostly use motors and battery options from a few major suppliers: Bosch, Yamaha, Shimano, and Brose. A few other brands exist, but are less reliable or powerful. Some, like the Yamaha system, have more torque and others are quieter. But generally all four make good options. Look for motor output (in watts) which will give you an idea of total power. But watt hours (Wh) is perhaps a better figure to use—it takes into account battery output and life to give a truer reflection of power.