I currently run Dropbox and think it's great. Only a couple of problems with it, space restriction unless you shell out quite a bit of money for what is just disk space and if your computer loses it's connection to the hard drive with all your dropbox files on it, it then tells you that it's removing all the files from the server, although it doesn't actually do it, that I've found anyway!
I also currently run Insync. Essentially it does exactly what dropbox does, but uses Google Docs storage area and syncs all my Google Docs. Space restriction still applies, but extra space is a lot cheaper and can be used for all things Google.
Certainly worth keeping an eye on Google Drive ... with much interest.