I was reluctant to brick my own iPhone, but thanks to David K. MacArthur of Fast Cash Pawnbrokers who FedExed me an unactivated iPhone from his large collection of pawned phones today, I decided to sit down with Shooby's excellent instructions and try iUnlock. It worked flawlessly the first time and I am sitting looking at an iPhone on T-Mobile. I just checked my voice mail: No Visual Voice Mail® - who cares - but it works swell!
Just as I finished, of course, iPhone Dev Team announced an all-in-one GUI unlock, so now it's even easier. I wonder if Scott Bourne will believe me? ;-)