How to share and use office files wilth multiple users: ProofHQ
"A new tool for designers (or anyone who needs client input on proofs) is premiering today. ProofHQ is a web-based application for uploading, annotating, commenting and approving proofs with controlled access for multiple clients. It's not Mac-specific, but it's worth mentioning considering the large portion of Mac users (and TUAW readers) who fit into the creative/design category. It doesn't work on the iPhone, (why would you want to upload and proof on an iPhone, really?), but it's fully Safari-compatible and Mac-friendly.
Using ProofHQ's upload page or the Java-based Uploadr, you can send PDF, PSD, GIF, TIFF, JPG, BMP, Word and Powerpoint files and have them converted into Flash-based proofs at full quality."
Thinkfree is another useful app - how to share files, update them, being updated by their servers. There is a big need to crack the multi user making alterations on 1 document. Google docs has had some work on it, but it's a tough problem. I'd imagine something this might be useful, but not probably implemented for various reasons. Defaulting back to Office, or not moving from it.