I agree that there is a lot of junk out there. I do have a couple of things to chime in on:
. Make sure the engine is secure with no less than 440 socket head screws into blind nuts with blue lock tight. Throw away anything metric that you can......
Actually, the finer threads on metric bolts make them better at handling vibration than something as corse as a 4-40. (Check out the nuts and bolts on all the helos out there). That said, most ARFs come with cheap hardware, and you will be well served to replace cheap crosspoint screws with quality socket head stuff, metric or english. Heck, a lot of guys I know (myself included) will removed the garbage bolts that come with a lot of engines, like the garbage OS ships as muffler bolts, and use better quality screws. A lot of guys pull the head bolts on their OS LA line engines and replace them as well. (The OS engine isn't garbage, but the muffler bolts on the smaller engines are. OS isn't the only company guilty of this either).
The MDS (Mostly Dead Stick) .40 is an engine with a known problem. The origional carb was a horrible design, and the manufacturer has now released a new carb design that totally fixes the engine. You can mail back your troublesome MDS .40 or just the carb for a replacement carb that will make the engine run quite well. I agree that OS engines are good engines. The Evolution engine is showing up a lot with my students, and is proving to also be a solid power plant. Thunder Tiger and Magnum are two lower price brands that run well.
The wings being held together with tape is actually quite common with a lot of basic trainers. They like to advertise that no glue is necessary. Apparently, someone in marketing decided that people are afraid of glue. Anyway, I've flown several planes with the wings held together just with tape, and haven't had a problem with them, with one exception. But I always recommend the owner glue the wing together.
Pushrods made with the 2-56-sized rod attached to a wooden dowl have been the norm for many many years on the smaller (.40 and under) planes. There is nothing wrong with this approach as long as the pushrods are assembled "correctly". Correctly means more than just some tape. The dowl should be groved and have a hole drilled crosswise. The metal rod should be wrapped with heatshrink tubing or thread and epoxy. You don't need 4-40 gear in a plane of that size, espeically a trainer, though there is no reason why you can't run 4-40 if you want to.