First let me mention that I bought a downtube a few months back to replace my commuting bike. I have been very pleased with it and even fitted a homebrew lighting system. I frequently tow a trailer and I ride every day regardless of weather. I have had two issues and one "failure."
1) The failure was corrosion/freezing brake and shifter wires/housings. This winter the shifting and braking starting degrading rapidly. If the weather ever got near freezing, the gd cables became almost unusably stiff. This is not unheard of - i have experienced this on other bike, but usually at much colder temps, and it could usually be corrected with lube/wd-40 squirted into the cable housing. That didn't work at all. I was never happy with the crappy sunrace gripshifter anyway, but as a result of the increased tension on the cables, the shifter unit actually just broke when I tried to make an upshift one morning. And when I say it broke, it literally came apart into three pieces on the bar. The happy ending is that I had a shimano 8 spd grip shifter with stainless cable that I installed and the whole bike is like a new (and better) machine. when I pulled out the old cable from the housing, it was badly corroded. Don't know what kind of material that cable's made of, but I have never seen one go south that quickly or that severely. I highly recommend a shifter/cable upgrade. brake cables, too. and by the way, with the new shifter and cables, freezing temps no longer incapacitate the drivetrain.
2) I also find that every time the temp gets near freezing, my headset stiffens up dramatically. This is almost certainly because whatever grease is in there is super, extremely crappy and has a very narrow functional temperature range. I have never encountered this before and only even heard of such a thing in ice-biking in the tundra. This is not a functionality issue, and re-building the headset is no small task, so I have decided to live with this for the time being.
3) Finally, my bottom bracket has developed noticeable play. I will be replacing it this weekend. This happened after about 3.5 months of riding - very poor indeed. Anyone know what size bottom bracket I need to buy?
Admittedly, this bike gets hard use (abuse?) from me, but I have abused other bikes equally with better results. I am still very happy with the bike, but just wanted to update my review of the bike because even though it's much less expensive than it's competitors, there is a reason. (Oh - it still rides great and the frame is rock solid. great bike, cheap as turd components.)