Yes. But the docs are still in the possession of Google and their staff. Admittedly 1024 & 2048 bit PGP encryption is a pretty tough nut to crack. And most likely documents encrypted in such a way would at this time be secure.
But if one is using this for business and one has to rely on others(IT illiterate staff) to actually encrypt data before giving it to Google could one be 100% certain that all sensitive data is in fact being properly encrypted.
What one ends up with is another layer of administration/policy/practice to add to a businesses current security measures, another potential point of failure.
For a single individual uploading his/her own data who encrypts first then yes the data maybe secure from prying eyes and remain confidential, but then there are the other two concepts of the CIA triad to consider namely integrity and availability.
I don't doubt Googles security professionals are far more skilled/knowledgeable than I but using Google for sensitive information, to me is a no no.