After moving from a non-slide camper to one with a nice big slide, I will never go back. I'm totally addicted to the extra space during those sub-optimal camping days even if it means a little more maintenance.
I realize stuff can always happen, but in my three years of camping around hundreds of slide outs, in various configurations, from trailers of various vintages, I have never seen anyone dealing with a major slide issue. I feel like I have assisted someone with almost every other component with a trailer at one point or another.
To me it seems like they are actually a pretty reliable component compared to some other items on trailers.