Most of my experiences have been fairly good. There was one time where the chicken schnitzel I ordered was served raw more than once though. Nobody wants to get salmonella.
Whether he's lying or not, a buddy of mine reckons he once saw a chef peeling prawns into a bucket while doing a number two at a hole in the wall Chinese takeout joint. (Guy went to the extent of using the public bathroom too.) Pretty sure that place would have been very short-lived.