I've had several bikes now, and a few electric bikes. So here's my view of what makes the best electric bike.
There's two main parts; the bike and the electrics. Let's start with the bike.
I prefer a folder, because I can get it in the back of my Landrover, without needing to put on a bike rack. And I like a folder that folds quickly and easily, of course. The one I use now, lets you put the handlebar downbar into a tube that holds the whole folded bike together. That's nice.
21 gears, because I'm doing rough ground and uphills. Actually 18 or 24 would be just as good; the important thing is to have a low bottom gear and a high top gear, and a few in between.
I think I'd like disc brakes. I currently have caliper brakes, and they work (and I get through a lot of brake pads), but I've heard that discs are better.
I use a bracket to mount the pda holder on. That's so I can put it on and off quickly; I found that leaving it on leads to it getting broken when I fold the bike and put it in the car.
A back carrier and saddlebags. The saddlebags carry all the tools I'll need to fix a puncture in the middle of nowhere, including a spare inner tube. Also water, and any other emergency stuff I might need, such as my head torch (that also has a red rear lamp).
The tires are kevlar-reinforced for puncture resistance, the inner tubes are the heavyweight puncture-resistant type, and I line the tire with a gel insert as a further puncture defence. I just don't get punctures.
I have front and rear shock absorbers. They're very cheap and not very good, but I think they do help a bit with the rough ground.
A bell; that's so I can politely warn walkers that I'm behind them and about to go past them. What I don't want, is a walker suddenly spotting me coming from behind them, and moving quickly in just the wrong direction so that I collide.
A wooden spatula, so I can get the worst of the mud off when the bike clogs with prehensile mud.
I carry a *substantial* bike lock in the saddlebags. If I go out without the saddlebags, I carry a smaller bike lock. And in the car, I have a *really* heavy-duty bike lock, in case I need to lock it somewhere risky. The reason I carry a bike lock, is that sometimes I want to chain the bike up and walk a couple of hundred yards, because the terrain to the cache is really bike-hostile.
Folding pedals, to help get the bike into the car. I prefer the type where you squeeze the pedal to fold it, rather than the type where you push the pedal in.
In the car, I carry a spare inner tube, a spare tire, more tools, spare pedals, spare head torch, electric pump, spare brake shoes.
Next, the electrics. I have a 250 watt motor. That's the legal maximum for road use in an electric bike. I'd really like 500 watts, or even 350, but heigh ho. This motor runs from a 24 volt, 10 amp-hour battery. So that's 240 watt-hours. What would be better, would be 36 volts and 10 AH, giving 360 watt-hours. Even better would be 36 volts and 16 AH, giving 576 watt-hours. You can even get 36 volt, 18 AH, giving 648 watt-hours, that's 2 1/2 times as much as the batteries I use now. And you can get 48 volt, 15 AH batteries that's 720 watt-hours, and that's probably the best you can now get, but not many people sell bike motors that run at 48 volts. These 48v, 15AH batteries weigh 5.8 kg; the 24v ones I use are 2.7 kg
I have three of those 24v 10AH batteries; I find that each one lasts 3 or 4 hours, but (of course) it depends on how much I make use of them. People often ask me "How far will it go", but the answer is, it's a bike, you can pedal it from Cornwall to Scotland. So far, I haven't exhausted all three batteries. Although I have failed to take enough batteries with me on a trip, and needed to pedal the last couple of miles.
By the way, batteries don't last for ever. When people extol the cheapness of the running of an electric bike, they don't usually take into consideration the cost of the batteries. I'd guess that if you use a battery every day, you might not get much more than two years out of it. They don't just fail, though - they gradually hold less and less charge.
The bike has a throttle. Some electric bikes use "pedelec", which means that the motor cuts in when you pedal, and stops when you stop pedalling. I prefer not to use that, I use a throttle. There's two types of throttle, the twist grip and the thumb throttle. I slightly prefer the thumb type, but the twist grip works fine.
I carry two pair of gloves; a very light pair of fingerless biking gloves, and a heavy sheepskin pair. When biking, I *always* wear gloves.
And helmets - I have three. One is a biking helmet with open slots, the kind most people use. The second is more wrap-around, it's the skateboarding-style of helmet. I use that when it's too cold for the first kind of helmet. And the third is a Biggles-style flying helmet; made of leather and fur lined. That's for *really* cold weather.
An electric bike is heavy! You have the weight of the bike, plus the weight of the electric motor, which is (roughtly) a solid block of copper. And the batteries are heavy; before I lift the bike over an obstacle (such as a gate), I take off the panniers (quick release panniers are a good idea), and sometimes remove the in-use battery too. If I've had to do a lot of lifting during the day, my back feels it! But many kissing gates can be negotiated by folding the bike.
You don't need insurance for an electric bike, and you can be quite young and still ride it; 14 is the minimum age. There's no upper limit. You don't need to take a driving test; for most legal purposes, an electric bike is pretty much the same as an pedal bike. I don't think a helmet is compulsory, but you'd be daft not to wear one. And gloves - I've come off the bike quite a few times, and if your hands are unprotected, you can get a nasty graze. I also like to wear my camo coat, for protection, unless it's really much too hot for that.
I hope this helps people thinking of going electric!