I think this is an interesting analysis, and as others have pointed out, it's unfair to complain that RescueTime user's are representative - the only thing RescueTime can comment on is what their user's are using.
However I think it is slightly misleading to include "Gmail" under the umbrella of "Google Apps" when comparing them to Microsoft Office. It would be fairer to only include the individual Google Docs apps compared to what is included in Microsoft Office.
Many Microsoft Office users might be using Gmail for personal mail simultaneously while not using any other Google Docs products.
However most users of Google Docs are likely not also using Outlook (in isolation of the other Office apps) for their email.
More and more users are being exposed to working with online software due to Gmail. If they compare it with Outlook, they might even find it superior. That does make it easier to sell people on the idea of Google apps.