I don't have a 360 of my own, but Gamerscore either way is meaningless to me. Even amazingly high numbers are worthless, honestly. The points are arbitrary and there's no way to tell if you got 1000 GS in 10 minutes of The Last Airbender or hundreds of hours of something else. You have to dig through all their achievements and that's just a time waster.
Honestly, I care about achievements, but not the way anyone's implemented them yet. I want a simple system: no numbers, no points, not even an overall achievement count. Give me the ability to show off maybe my favorite 10 achievements on my gamercard or something. Only a few achievements ever actually felt like I accomplished something other than wasting time or grinding, so give me a way to communicate the ones I liked.