Everyone has a different definition of what they consider to be reliable quality components based upon their expectations.
I personally am not a fan of the China Girl type 2-stroke motors that are made out of Chinacheapoesium metal. I prefer a micro 4-stroke engine like they use on upper end commercial grade lawn equipment such as string trimmers and back-pack blowers (Note: I said upper end commercial duty equipment. I'm not talking about those cheapo $99 special Wal-mart sale string trimmers and the motors used in them). I prefer a good solid chain drive (driving the hub not just bolted to the darn spokes !!!) where there is no flimsy chain tensioner to break, bend or wear out and instead prefer an adjustable motor mount where you loosen the mounts for the motor or the gear box attached to the motor and slide it back to give just barely enough chain slack to work the chain on or off and then slide the mounts back up to tighten the chain and then tighten down the mounting bolts tight. No chain tensioner needed.
I've never had a real affection for coaster brakes but much prefer a quality set of V-pull brakes with high end performance pads or better yet disk brakes with quality calipers and pads.
As far as the bike itself so long as it is built sturdy enough and isn't brittle I'm mainly looking at how its geometry is set-up and all the finer details such as how it is set-up as far as component compatibility (brake mounts available, bottom bracket type, head type, derail-er mounting configuration, fender mounting, cargo rack mounting, etc . . .).
Hopefully fairly soon I'm going to be making my own frames from stainless steel square tube. Getting set-up for that right now so I can make what I want how I want it. Using stock frames is just getting too limiting even with doing hack-and-weld jobs on them to get them to suit my needs and I don't want to pay thousands upon thousands of dollars to custom frame builders and I've got more time then money especially when school is out for three months in the summer and about a month long break starting a little before Christmas and going through the first half of every January. My student days are over but I work two jobs and one of them is at a school so when school is out my work is cut in half with only one of my two jobs being active and my open time for projects doubles.