Uploading some of Office's lesser document types in a workspace works fine. However, if there is no viewer then you have to click each file to be able to save the file to disk.

 I.E. Add 4 faxes that have been scanned with Office Document Imaging - .mdi files. Even though you can check the 4 files, you have to click a single one to see there's no registered viewer with them and then save them to disk. You can't save all 4 files at once (although you can upload them at once).

 This may be a case where I'm using the product in ways not really intended... Office Live seems to be SharePoint for the masses, and the functionality I want is more Live Mesh (I'm guessing by name alone, Groove for the masses?)