It is important to remember that the mtgox btc valuation is artificially high because of them being blacklisted by as much of the fiat banking system the USG can influence. So, transferring the btc to another exchange and selling it is only realizing what the btc are really worth.
It's also important to realize that prices on other exchanges which are less impacted by the aformentioned harassment, or are perceived to be, are used by persons who are under more pressure to make sales and are thus the spot price is likely depressed. So 'are really worth' is not likely to be an entirely accurate statement either.
The best option to get fiat is to buy btc on mtgox and sell on localbitcoins where the prices are good, or, if in a hurry, sell on bitstamp instead.
Or at least sell by some other means. Bitcoin-brokers.org being no longer an option for me, I choose Coinbase and am so far pretty happy with the decision. My experimental sale was between Mt. Gox and Bitstamp pricing while the first installment of my real sale came in closer to Bitstamp spot (though still notably above.) Another cool thing is that USD goes directly into a bank account so I don't have to dick with withdraw requests, wire fees, USPS parcels full of green, meeting people to exchange chump-change, etc.
Best, however, is that I did not seem to have to entrust my identity docs to Coinbase. Since, unlike Bitstamp, Coinbase uses real names and don't seem to use domain cloaking and foreign shell companies I would have done so, but it turned out that it was not necessary. Yet.