Personally I find it a good way to spend in the US. I bank with HSBC and find that even with the various charges involved, the end result - ie the amount in sterling on my bank statement for each transaction, converted to work out the exchange rate - compares favourably with exchange rates on credit cards or when buying cash.
I think perhaps that the various charges etc put people off and make it seem a bad option when that may not necessarily be the case. But, as with everything, I always look at the total overall cost, and for me using my debit card works out better financially. I certainly would not do it if it didn't work in my favour - I'm Yorkshire born and bred!