I've put almost 250 miles on it so far, usually in 15-mile trips to the coast and back.
There've been some issues with a balky coaster brake; issues that would have been the same with or without the motor, ironically. Bent the frame from one of the brake incidents and I didn't slam the brake on... I've since rebuilt the brake and after banging the chainstay and seatstay back into shape, so far, so good.
There's been some motor chain rub on the rear tire that's been happening since day one; that should be solved with the installation of the proper rag joint mounting gaskets at the rear sprocket spacing the chain a little farther outboard and the use of narrower KMC BMX chain instead of the wider-than-necessary kit chain. The motor drive sprocket is now narrowed for the BMX chain.
Finally, the cheesy but effective side-pull caliper front brake flexes a bunch, pointing the longer, softer brake shoes upward into the front tire... LOL. A realign of the shoes seems to have solved that problem... all's good now that I've butchered two new tires. Hahaha... The motor itself and it's peripherals have been trouble-free.
I'm looking forward to getting to meet more motored bike enthusiasts here.
Until then... may your plugs never foul.