They turn out some "not so pretty looking" flints, but they are usually pretty solid performers for me. I find that even with an uneven sharp edge, one or two drops into the frizzen and they're good to go.
I just changed out a Neolithics flint that had about 40-50 shots on it. Maybe not a super high amount, but at less than 2 bucks a flint delivered, I can buy nearly 2 of them for the cost of one off the shelf at a shop.