Thanks for the feedback, everyone, including the lessons on Chinese history.

There are enough reasons for me to avoid the stock 6-speed setup. Shifting is kludgy, as every gear up or down is two shifts (thanks tcs for pointing out how the shifting works). The derailleur easily collects road grime (thanks EM42 for pointing that out). And the extra gear range just isn't that much more than the 5-speed to offset these disadvantages.

I'm going to buy a 3-speed and spend a couple of hundred bucks to switch it over to a 5-speed with a new rear wheel and shifter. That way I can switch back if for some reason the 5-speed hub turns out not to be a good idea. In that case I might look at a Schlumpf Mountain Drive setup like tcs described, which has a great gear range.

Thanks again for all the useful feedback!