Tom I'm learning as I go primarily from others that are do it yourself advocates. Basic battery & controller guidelines and operation parameters with varying motor outputs is foundational material to build on. Charging guidelines for lithium based packs and safety guidelines for their safe & long term use, maintenance and storage is also vital information for all who are thinking about e-bikes.
All that said manufacturers hype and other promotional material can be taken with a grain of salt & that chased with much research and some Jesuit logic. The basics of frame design with internal combustion engines or straight pedal power aren't changed by using a e-motor and battery pack drive. Balance, weight & center of gravity (physics) of the Newtonian variety aren't altered by the selected power source, other than by magnitude, i.e. 10 kw output is greater than 3 kw output regardless of using gas or battery power. So if you understand how gas bike frames and components work you've got a huge leg up on building an e-bike that will actually work.
I'd say e-bikes built to high performance standards like Jeff and Pat build are gems...period! Unique style and high performance of hand built e-bikes or gas come at a premium which can be justified. Specialized downhill racer bikes also come at a premium that is understandable. However off the shelf bikes with 250 watt to 500 watt motors and good battery packs & controllers costing many thousands because they have mid drive, Kevlar belts, 3 speed hub, hidden in frame battery, lightweight frames etc. etc.; are mostly smoke and mirrors to charge more for 25 to 35 mph & 50 to 70 kilometers of range. Not good performance to value ratio in my economic world view, just brand name, slick tricks & buzzword hype.
I do see the road legal,under $2,000. to $2,500. mass produced e-bikes having a legitimate place in the market....
In the meantime I'm just sticking to the simple tried and true while picking up more information.
Rick C.
