Oddly, hybrids seem to be really reliable, despite the additional stuff to break. Priuses get top marks for reliability. I'm not sure why, but I imagine it comes down to the electric stuff being extremely reliable due to the nature of the beast, and the gasoline end being treated more nicely (more consistent RPMs and throttle settings, no idling, not being used at all for a substantial fraction of your miles) more than compensates for the tiny increase in potential failures from adding the electric system. Also consider that there is essentially no transmission in the more advanced hybrids, which removes a potentially expensive breakage that regular gas cars are subject to.