I attended a briefing today on Google Apps. Google is celebrating over 1 million business customers in EMEA (Europe, Middle East and Africa) since the launch of Google Apps just over 4 years ago, and over 3 million worldwide. An unknown proportion of those customers are small businesses using the free edition; but there are some well-known names which have signed up, including Rentokil Initial, Virgin America, Motorola, The Guardian, The Telegraph, and Jaguar Landrover.
The big announcement today is called Discussions in Google Docs, and I have had a quick try with a short document that I opened for discussion. One thing I learned is that if you want to allow public discussion on a document, you have to make it world-editable (like a wiki). It should be possible to have the document locked but still enable comments, but I cannot see how to do that; it seems that leaving a comment requires the same rights as editing the document.
Another oddity is that there are two comment panels, a narrow column on the right
and a big blue panel that appears if you select Show Discussions from the top menu.
If you are logged in, you can request notifications by email and even add comments by replying to email notifications.
There is also a per-comment feature mysteriously called Resolve. A resolved comment is semi-deleted; it is removed from the comment stream (narrow panel) but still appears in the full discussion (big blue panel).
My snap judgment is that these comments/discussions will be useful for document collaboration, which is already among the strongest features of Google Apps.