Optical drives fail, always have. That said, in my experience slot loaders are slightly more prone to dust buildup than tray loading drives; my MBP got to the point it wouldn't reliably read discs after about two years, but after being cleaned it's fine. Lost a slot-loading drive at work to dust as well, but that one is located in a machine shop so is exposed to ridiculous amounts of dust.
Otherwise I haven't noticed a failure rate any higher on the drives Apple uses than any other manufacturer.