We used our Lloyds TSB debit card in the ATM machines in July and were charged $2.00 by the US bank per transaction and a further £2.00 by LloydsTSB. The rate of exchange was pretty good though.
The main thing to remember is not to take out lots of small amounts. We take out a few hundred dollars at a time to minimise the charges. We then pay for bills etc by credit card which goes straight through with no charges (although, unless kept in check this can provide for a nasty shock when the bill arrives at home!!) IMHO it is still easier and safer to do this than to carry large amounts of cash or TC's.