Given Google's obvious prowess with servers, I'm actually amazed Google drive isn't better than it is.
I store everything on there including JPGs, AVCHD videos, TrueCrypt volumes and every other kind of file type. Never had a single sync issue or slow sync speed.
OneDrive (formerly SkyDrive) on the other hand... That constantly left filename.machinename split versions and the sync speed was uselessly slow.
One can easily argue though that, Google Drive may make a change which breaks insync - but for past year and half, I have had zero problems.
Also, Google Drive misses some basic functionality, like getting an actual list of of shared folders and with whom they were shared [1]. Instead you have to check every folder manually.
[1] http://webapps.stackexchange.com/questions/46135/how-can-i-s...
If I empty out both drives and start from scratch, then put the same files in both, it seems to take Google Drive around 350% time to sync the same files.
Saying that, as a paying customer, I still love Dropbox since it's sync quality & ease is outstanding. I'm also a fan of their Datastore API.
Microsoft's Onedrive has been surprisingly good for me - on Android as well.
The OS X client is passable, and the fact that you can't do things like LAN sync or rate limit the upload speed make it no good for many clients of mine.