When you have a 20-cell battery, you only get about 80% of the theoretical capacity because of the higher current per cell, so 200Wh on a fairly light efficient bike would give you between 20 to 40 miles, depending on how hard you pedal and how steep the hills are. They have the optional Xtra bottle battery to double that range if you need it.
I think the whole concept is really good. It looks like one of the few OEM bikes that I'd like to own, but it's way to expensive for what it is. £2000 - £2500 would be more like it. At £2000, I'd buy one.