Other than my wife's Christmas cake, my dad's Christmas Trifle and Esther's Banoffee Pie, very little (that I want to discuss in public) makes me happier than extended LF.
Obviously all good things need to be used in moderation and very carefully. I have not always managed this which explains my weight - both physical and tonewise on occasion.
The space proper bottom end needs to breath means that it is impossible to monitor what is hitting the punters between the eyes when you are onstage, so yes, very careful set up and monitoring is imperative.
BUT, all these things considered - a properly crossed-over sub will take over the heavy lifting from a cab on a pole kind of cab and will increase the headroom for those louder gigs. I am not sitting here saying everyone should get a sub, and in 98% of situations it would be superfluous. But the other 2% are lots of fun