I've done a lot of transactions here on NS, and unfortunately this was the worst experience of them all. I had somewhat of a similar situation as Magnus, but thankfully mine ended a little bit better.
I bought a Salomon Gore-Tex kit off him for a bangin' deal of $140. He's in Denver, and I'm in Grand Junction (a 4 hour drive away), so I figured it should have shipped pretty quick. Well, 3 weeks passed and nothing showed up, and during that time he was fairly unresponsive to my PMs. I emailed him, and he said he sent it via USPS flat rate priority and he didn't know why it hadn't gotten there. He couldn't provide me a tracking number, but I learned from my local PO that all priority flat rate shipments now include a tracking number in the price. So at that point I politely asked for a refund and he was willing to do it. A couple days later nothing had happened, but he emailed me saying USPS had sent it back to him and he was reshipping via FedEx. This time he provided me with a tracking number, and the package arrived on the second day.
I am happy that my gear finally showed up and that I got it for such a great price. The shipping process was rather frustrating, but I'm just glad I didn't have to go hunt this guy down.
BOTTOM LINE: HIS PRICES ARE GOOD; COMMUNICATION, NOT SO MUCH. IF YOU DO BUY FROM HIM, BE ABSOLUTELY CRYSTAL CLEAR ON THE SHIPPING DETAILS AND BE SURE TO GET A TRACKING NUMBER FROM HIM.