There's a big difference between "impossible", and merely "impossible to be productive"! The latter is what the question mentions. And when I deny that this is

There's a big difference between "impossible", and merely "impossible to be productive"! The latter is what the question mentions. And when I deny that this is the case, the sort of thing I'm denying is that people who use (say) Mac OS X for developing their iOS programs would find it impossible to be productive, were they suddenly to find themselves forced into using (say) Windows to write things for the Xbox360. Oh well - perhaps my reading of the question is wrong, but this is very strongly what it implies to me.