I'm paying off a little disagreement I had with the IRS by credit card. I agree, it's usually not worth it.
But, my Hilton AMEX gives three points/dollar, and the convenience fee is 2.49%. Works out to 0.83 cents/point, which is less that Hilton charges.
If you're getting 1 mile/dollar, like most cards, it comes in at 2.49 cents/mile which is not a good deal.