While some of the ideas are great, the overall experience was pretty bad. Leaving autosave on often slowed down Word to an unworkable pace and after a few other issues (I'm not exactly sure what, wasn't involved) we just made sure only one person at a time works on the document.
Some other annoying small issues I experienced: when working together sometimes your undo history is gone. I guess that's because someone else edited too and correctly undoing something someone else edited in between is not simple. IMO it's impossible and any system doing merges automatically will fall apart at some point.
Track edits cannot track deleting rows of a table
Wed based word works actually pretty fine, but it misses random features. Adding captions seems not to be supported.