Has anyone done a front drive?
I've ridden one. http://syonyk.blogspot.com/2015/09/schwinn-tailwind-review-in-2015.html
this seems like a pretty affordable option. What are the downsides?
1. You can't use a front hub drive with suspension forks unless they're designed for it. Which is to say, don't use a front hub drive with suspension forks.
2. The handling is goofy at best. Bike geometries are not designed for power through the front wheel. Handling gets vague and rather dangerous depending on the power and geometry - much like how a high power front wheel drive car is weird under power, the bike will do the same thing.
3. You run a much higher risk of spinning the wheel up from the power if it's wet or slick out.
If you are going to do it, make sure you use non-suspension forks and good torque arms. If your front hub tears the dropouts up and falls out, you're going to crash, probably quite violently and painfully. Front wheel failures are no fun at all, from what I hear.
If you live in a very flat area and are willing to go with a 250W kit or so (max), it's borderline acceptable, but it's still not a good general solution.
I rode one for several years, including a daily bike commuter and towing a trailer with kids in it up hills.
It was terrific. Low cost and a lot of power. Ran on the lead acid battery for at least 30 minutes, and hour with pedalling. Batteries today are so much better, too.
Disadvantages (which is why we are building a mid drive bike now):
Heavy front wheel -- I wasn't jumping a full 4 inch square curb or large roots on trails anymore.
When the battery is dead, there is a lot of internal rolling resistance in the hub motor (front or back).
Our kit had a lot of wires zap strapped to our bike frame (it was a kit, so no wires fed from through the tubes).
BUT Advantages-- it was under $500, simple to install and operate, we installed on an existing bike, all the normal bike accessories worked (paniers, trailer, trail a bike). The hub motor is so quiet, and it had lots of power. Hub motor is enclosed so dirt, sand and puddles are not a problem. Simple to shift gears and less gear shifting needed.