Thought I'd provide an update:
Has been about a month.
Sales are steady, with only a single hiccup courtesy of AusPost delays.
I'm shipping all orders within 24-48 hours.
Biggest client has been a telco
Major competitors are expansys and ebay.
Tried one-to-one marketing on twitter, didn't work out to be effective.
Major advantages are search ranking (to an extent) and customer service.
Managed to luck out on quite a few other things that didn't seem so
important a month ago when I started, but now when I think about it, seems
miraculous.
Need to streamline a few processes.

Has distracted my focus from other dev-worthy domains, not to mention the drops. So I think I'll hold off on developing product domains in the interim. Too risky.