Yeah, I've sold a few bikes on ebay, and normally fix everything up, adjusting the derailleurs and oil the bike before I sell, ... the bikes end up pretty smooth and pleasant. But my old "department store bike", I was trying for ages to adjust the gears, and I think in the end I just made it worser. Its amazing how bad the quality is.
I think for affordable bikes, singlespeed roadsters are the way to go, they would eliminate most of the components that cause trouble on cheap bikes, and be much more efficient (even with the singlespeed), and of course, a joy to ride.