G'Day Peter and welcome to LAVA - it's great to have you here! For those who don't know Peter, he is the founder and president of Bloomy Controls and is a published LabVIEW author - a great resource for us here at LAVA
I very very rarely use them - usually when I'm trying to tech someone else a technique and need to fill in the blanks quickly. I never use them in production code. I tired to once (a long time ago, and maybe things have improved since then, but I haven't had a need to go back since), but needed to modify one of them a little, so I opened one of them up and was spooked by the horribly inefficient and amaturish code inside - it was quicker (and safer) to code what I was doing from scratch.