I've got two. A big Dutch Gazelle - T2i Ultimate. It has the Nyon system, which is basically a bike satnav. It's a belter. I've also had my Brompton converted to electric, too. The thing about having an electric bike is that it takes the grunt out of cycling. Any hill, and that's any hill round here at Littleborough is tamed. My favourite is to take Blackstone Edge and hope there's a roadie at the back end of his ride and I'll shove my Gazelle into turbo, sail past and say "Oooooh, this is a tough 'un!" And vanish!
The think you need to consider is the range the battery gives you. I get about 50 miles but that will vary depending on the terrain. I'll get less than 20 if I had to cycle all of the juice up Blackstone Edge until it ran out, but on the flat if yer faced with a howling 'breeze' yer can get the full whack of 45-50miles. It runs off a big Polish Bosch battery that has something well over 900 charges left in it. It charges in an hour or so but I never really let it get down to rock bottom.
The electric Brompton is a delight. it runs off a Bosch battery that charges power tools! I've not put the Brompton to the full test but I'm under the impression it's not gonna let me down! And I have a spare!
I got a bit of change out of £3k for the Gazelle, and the conversion cost me about a grand.
Electric bikes are the way forward. And for those unfamilar with the beasts you still have to pedal to get the juice. Stop pedalling and there's no power and apply the brakes and it cuts off the power. Go over 25kph and the electricity supply is cut off! I have a carbon road bike, a hybrid and each of them delivers their own special ride.