hmm.. that would differ from person to person. 'Eat your own dog food' it's called, iirc. If the programmer in question is also a hardcore gamer, then the programmer ought to know the goods and bads of gaming in general.
True. However i was more refering to final product testing. I was just quoting that golden rule from college that noone should do final testing on their own programs (not just games).
Its usually stupid little things that are so obvious or invisible to you as you have spent months living with the product, but someone new may be completely bewildered (eg, controls, rules etc). Also other people may have a different style of playing to you and may find bugs that you never would as it has been designed around your own logical idea of how things should progress in the game.