On the whole 1,000,000 gamerscore race, wouldn't you have to play at least 1,000 games on Live in order to do that? Are there even that many games available on Xbox 360?
Also, I wonder if any of those people have tried also playing the PC versions of games that use GFWL. GFWL achievement points count towards your Xbox Gamertag. If you play a game on 360, and the PC version of that game uses GFWL, you can get the same achievements twice by playing both versions.