Google Drive: It's Real and It's Live Now!

It's official:  Google Drive is live now.  You get 5 GB free.

This is what the competition offers:

• iCloud: 5 GB
• SkyDrive:  7 GB
• Dropbox:  2 GB (but you can increase this if you get friends to sign up)
• Box.com:  5 GB (though some like Touchpad users have 50 GB)

Which do you prefer and does standalone companies like Box and Dropbox have a shot against the mobile giants?