Till now I have a very good record with f3 against the Benko but since the book "DW Benoni and Benko" is out, I can see that more people are starting to play c4 with black and it is not easy to counter (but that's on the internet).
In "serious" games, I never have had to do with the Queen sacrifice or the "DW-variation".
My impression is that many black players are not enough prepared to encouter the Dlugy variation. Perhaps because it is not so modious any more?