I totally agree with all of the above, and that you can take great photos with cheap equipment. Just to play devil's advocate though...
What if you took a photographer that takes pretty good photos with a 600D + Kit lens and handed them a 1ds with an 85 1.2? I've gotta say that the quality of my images went up dramatically when I bought my first DSLR
Of course, the rub of the whole statement is "only as good as", when there are many tricks you can do with lighting/post production to squeeze better images out of devices that weren't designed with those uses in mind. I've seen many examples of studio photographers using their iphone to take great pictures. On the other hand, they used thousands of dollars worth of studio lighting + makeup artists, so to me, it kind of undermines their point.
All things being equal, the same photographer will take better pictures with better equipment 9 times out of 10. We all know this or we wouldn't even bother buying more equipment (except of course to show off our new equipment)
Anyway, in a general sense, I agree with all of you, but I think there is still a grain of truth in Nikon's statement.