I have never bought / sell ... but looking at that link ... he makes 30% just being the middle man. He buys at -15%, sells at +15%. I think that's totally unreasonable. Well, at least I don't think MtGox charges that much or any other exchanges for that matter.
In addition, it's craigslist ... I would be really be careful.

I hope you don't fall into the hype of record prices. And if you are into btc for the long term, what's another few days over the normal verified / trusted exchanges.

Like I said, I have never traded, so I'm not "encouraging" you to go one way or the other. Plus, it's your $$; do what floats your boat with it.