When I have to double authenticate in order to play Diablo 3, but I don't for all my data, I find that odd.
After syncing, the GDrive client constantly used almost 500MB (yes, 0.5GB) of memory while Dropbox was always under 50MB (Windows 7)[1]. That's a huge deal for a program that's supposed to be always running.
Also, the GDrive client often crashed while syncing and had problems syncing some weirdly named files that Dropbox handled perfectly.
I hope GDrive gets over these issues soon, since they have some cool features (e.g. webapp integration, content-based image indexing).
The (up) sync time was also about 10 times that of Dropbox.
Maybe they've fixed things, but the experience was pretty horrible all around.