A properly executed conversion is going to work just as well, maybe better, than any low cost new bike like one of the bd offerings. Some of the components on the bd bikes like the pedals, headsets and saddles are pretty much junk that you'd want to replace, not to mention random cases of defective parts. The cranksets are all road cranksets with short chainring bolts, rather than true single speed cranks. In effect, they are conversions and adaptations, rather than SS designs from the ground up. There is nothing especially complicated or unique about a SS that cannot be easily replicated with a conversion.