This is generally terrific news. Google Docs is already great, but the learning curve has been tough for those unaccustomed to working in the cloud. The new interface and collaboration tools will ease that sell, I think.
Besides using a new infrastructure, the document editor and the spreadsheet editor will add many new features. The document editor has real-time editing, sidebar chat, a new commenting system, better formatting and an improved importing feature. The spreadsheet editor brings back auto-complete, adds a formula bar for editing cells and you can now drag and drop columns.