Google Drive is now official and real, see the press release.

Surprisingly good is the low upgrade prices for those who want to use more than the free 5GB:

• 25GB for $2.49/month
• 100GB for $4.99/month
• 1TB for $49.99/month

Google Drive is therefore cheaper than Amazon S3 (prices here), although Amazon is targeted at enterprise customers, who are much more likely to use up their full allowance.

And substantially cheaper than DropBox.