lets face it those of on here that are more than comfy with the radio tits up, the transponder tits up, the alternator tits up, the starter motor tits up
The radio and transponder (and navaids come to that) wouldn't bother me (in VMC) (except that I'd be mildly irritated that I wasn't getting what I was paying the rental for). An alternator failure would probably make me return home. A starter motor failure would prompt the response "you must be joking, find me another one".