I don't understand the head-banging, to be honest. From what's been posted here, SD determined there was an issue in less than 24 hours, offered their apologies, and said the faulty recorder could either be exchanged for a new one or repaired at the buyer's discretion. I know it is frustrating to get a defective item, but it's always a possibility with almost any purchase and SD's customer service seems to have done all that you could expect from them.
Personally, I would also prefer a replacement, but I'd note that there is a potential benefit to sending it in for repair, which is that they carefully test the whole system before they return it. Once, I returned a piece of gear due to a faulty jack and, when it came back, I noticed that there were a bunch of other items listed on the invoice, including replacement of the knobs. I e-mailed them to say that I had no problems with the knobs and was curious why they had been replaced. SD explained that they had to pull them off with pliers to open the chassis and they were scuffed up a bit by that, so they replaced them. I don't have a ton of experience with their customer service, but they have been great when I did use them...