M$ are big on tying people into their formats. I'm an Xbox player on Live but I can see friends getting achievements on PCs and Windows smart phones. M$ are really pushing the convergence without putting much effort into the user experience.
In better news Xbox Live is a really good service after being iteratively updated, so the same may happen for GFWL.
GFWL
In better news Xbox Live is a really good service after being iteratively updated, so the same may happen for GFWL.