I have used this plugin on an intranet-type collab site for almost a year.
It's not quite G.... Docs in WP /BP, but if you can't or won't use that service, then this plugin is probably your best option.
It's solid and reliable. I've only had one real issue and it was solved with amazing support.
The plugin author has deep BP knowledge and it shows in the quality of the plugin (make sure to check out his other plugins!).