I briefly considered switching to Google Drive when it was released. I copied all the files in my Dropbox (57GB) to the GDrive folder and waited for everything to sync.
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).