I have been using regexp daily for 8 years now and I have opinions. The most controversial one is that writing regexp to do things in production code is like using dynamite to take care of an ant hill.
I often see regexp used because it is so versatile and can perform very complex operations. But, regexp is hard to think about and therefore dangerous. You need a clear head and mental focus and years and years of experience to use it and even then you may still blow off your arm.
Bottom line is that in prod regexp should really be seen as a tool of last resort rather than the first thing you look to.
Given that, where exactly am I using regexp daily? I just use it locally for development in the safety of source control where I can easily revert my mistakes. :)