Entrusting your money to a web site registered to a PO Box in the West Indies with numerous complaints of theft is a bad idea. It really looks like their business model is to steal accounts, just not all of them at once (since that would make it too obvious that they were a scam all along).
Using an "online wallet service" is a terrible idea. You're entrusting your money to an anonymous scammer.
That's what I thought at first, but I ended up using mybitcoin.com afterall. They do provide a very useful service: instant irreversible transactions between accounts.
If I meet someone at a coffeeshop for a cash transaction, and the bitcoin have been placed in a mybitcoin account ahead of time, then the whole exchange takes only a few seconds. The received bitcoin can be automatically forwarded to your home address for the hour-long transfer -- long after you've left the coffeeshop. Both sides have only a small amount on mybitcoin, and only for a short time (a few hours). And you get a timestamped email to remember the exact details.
That said, if the person you're dealing with doesn't look very shady, it's quite safe to only wait for the first confirmation. Ten minutes or so isn't that big of a deal.
With mybitcoin.com, you should understand that you're not dealing with an established company with 1000 employees. You're dealing with a guy. Or at most a small group of guys. Customer service probably isn't going to be a strength for quite some time (if ever).
My impression is that he knows a lot about computer security. Clearly he is not a rank amateur -- read this statement on the Mt.Gox fiasco: https://www.mybitcoin.com/downloads/incident-report-2011-06-22.txt
He also knows something about protecting anonymity. He's probably an American or Canadian who has set up shop offshore in order to protect himself against the coming government backlash. I can respect that.
These are still early days for the bitcoin movement. Perhaps mybitcoin.com will end up only serving those who really need anonymity, and other services will emerge to provide instant transactions with a friendlier (and probably less secure) interface. Let's not jump to conclusions, either way.
Tom Williams: Understand that your company's reputation is more important than the technical details you're busily working on right now. Don't sacrifice one for the other. Respond to this issue immediately, and resolve it to lettucebee's satisfaction.