Honestly... I've never known many devs that play their own games. They'll tell you they do to make you feel more at ease, and surely they do to an extent but generally not in the capacity that a normal player does. This is why they have in-house testers. Although it depends on the area of development that the "dev" is in that usually determines whether or not they play./ More creative departments have a much higher frequency of playtime in my experience where as core systems and programmers don't spend too much time. Personally for me, it has always been knowing how everything works behind the scenes that usually kills it for me.