With some judicious planning, credit cards are a way of making money. Say you have a £2000 bill on your credit card. By switching it to a 0% on balance transfers for a 12 month period, and saving the £2000 in a high interest bearing savings account, you make money, even with transfer fees. For instance, if the fee is 2% of the transfer balance, your paying £40 on the £2000 bill. If you save £2000-£40 = £1960 in a 6% AER account, you make about £117 overall. All the while, you've bought whatever it was you earned the bill for.
Of course, this requires discipline and planning, but that shouldn't be a problem for the disciplined readership of RR, right?
The same canny thing is done with the 0% to pay offers on furniture. Divide the total bill be 12, pay that 1/12th into a savings account each month and you get the balance to pay off the bill at the end, and the interest pays for a meal for you and the missus. Quids in!