The shop that I managed used all BOA system boots for rentals our first year. Customers loved them, and the BOA system held up extremely well, considering how many days those boots saw. When there was a BOA issue, we could fix it in about 5 minutes. Most of the time the boot itself failed before the cable or BOA mechanism. Most of the BOA equipped boots that I have seen come with a replacement cable and the little allen key necessary for the repair. If the mechanism goes south, thats a bit more of an issue. I certainly wouldn't shy away from a boot because of BOA and I prefer the dual zone BOA boots ('cause I have really narrow feet).
I always found it interesting that so many customers who were looking at purchasing boots had the "what do I do if it breaks" question, yet very few customers looking at Flow bindings asked the same question.