Recently I've come across the expression "... to cut the mustard" fairly often. As with all of these phrases, once I've gathered their meaning, I start using them. My wife was amused and delighted when I used it the other morning.
I've just done a bit of research on it as I wasn't completely sure what the meaning of it is or where the expression comes from. The truth is, there seems to be more than one explanation/origin of the phrase. Here is a link sporting some of the various attempts to shed some light on its origin.