I think the new layout is one of the preparations of the launch of Google's Presentation Service
It also seems to me that the new layout of GDocs became more similar to "Microsoft-like" layouts such as Windows Live Mail or Outlook Web Access, with a navigation bar on the left and also with the special effects when moving the mouse over the buttons. But still it is intuitive and easy to overlook.
Why use such "online office systems"? It's just for playing around but nothing productive!
I think that is one of the most statements users give. I personally used such services very rarely till now, also because you don't need it just for yourself. Intuitively you will use your local hard disk to save your documents etc...The point is that services like GDocs may only be useful if you have data that you want to share with other people. Assume you're working on a project where more people are working on different things. In such a case GDocs may be useful, also because the usual versioning systems like Subversion or CVS are more for text-files and source-files (which are basically text-files) as for rich text documents. In such situation it may be the right moment to use online office systems.
Recently, when I started to set-up some documents on GDocs in preparation for a project I'm doing, I noticed that an extremely nice feature or better feature update would be to have the possibility of sharing entire folders or at least multiple files at the same time. The idea would be to have a folder which is shared with more people and every document which is put inside that folder, will be automatically shared with all of them. That would be much more useful than only being able to share document by document.