The complaints are almost universally dated, and many of them refer to penny auction practices, which was NMR's original business model (now dropped.)
Although there seem to also be a lot of complaints about product quality and customer service, many are also dated and you have to keep the volume NMR does in context -- they're estimated to have exceeded $125 million in volume this year, which is huge for a relatively new site in the "daily deals" niche. They also just received a $12 million investment into the company from GMarket, which is itself part of eBay (Link hidden: Login to view
On the other hand, the T&C on the site expressly forbids reselling. Now, how on earth they would ever keep track of that is anybody's guess. But for whatever reason, they don't want customers reselling the stuff they buy there.