Not a good experience...
I had contacted Whitney about the HP-2s he bought from Recstar24 above to let him know that I'd be interested if he were to consider selling them. A week later he PMed to let me know that he doesn't like the way they sound and he'd sell them to me. He quoted a price that I agreed to. Then he stalled as it came time to pay and told me he wanted to wait until after the weekend and for me to pay on Monday. The following happened over the weekend:
1. I sell a mint vintage Breitling watch to aggregate funds for this purchase and to pay him promptly.
2. I allow an eBay auction to go by where the HP-2 was won for only $811! I didn't bid because I was honoring my commitment.
Meanwhile he ignores my PMs to obtain shipping address for the payment...and continues to post on Head-Fi as if nothing had happened. Completely unresponsive.
EDIT: After the frustrating events above, I was fortunate that another Head-Fier had a very nice pair for sale and ended up closing the transaction with him. I mean I literally had the cash in my pocket for a couple of days as I awaited Rhythmdevils' response and was ready to go to the post office and get an MO.
Rhythmdevils finally contacted me almost 2 weeks later (again, he's read my PMs and had been posting the entire time) and told me that he "spaced" out.

But I did appreciate that at least he acknowledged what had happened. But I had also found out he had pulled out of at least one other transaction for another item before.

EDIT #2: Voltron, I had
3! PMs where I asked for Whitney's payment information. The first one was ignored and he simply responded to other parts of my PM. For the second one he suggested he wanted to wait the weekend. The third on on Monday he simply didn't write back to me at all. You figure it out.
EDIT #3: I would also like to emphasise that Whitney didn't swindle me out of money or anything and he is a nice guy. But similar to what Episiarch said below is he just has a tendency to waffle on transactions and doesn't make a full commitment. I believe with these posts he will be more resolute when it comes to future dealings.