I'm wondering if there is clean way to co-author with the Excel 2010 desktop App? Now, or possibly this could be a placeholder for the future. The current answer seems to be no with Excel 2010 desktop using SkyDrive, but maybe with Google Cloud Connect. But many of those posts are over a year old.
The background I have so far...
I'm talking about doing this with the Excel 2010 desktop app (not web app): How to use Office 2010's co-authoring tools?
But for some reason MS went sideways and only put co-authoring into the Excel web app (which is the reverse of what they did with Word). It does seem you can do file-level updates against SkyDrive. http://currents.michaelsampson.net/2010/02/coauthoring-in-excel-2010-not-supported-use-the-excel-web-app-instead.html http://www.boxless.com.au/2011/google-docs-and-cloud-connect-is-now-useful/
Google Cloud Connect seems a possibility, but reports are mixed. Is anyone using it successfully? http://arstechnica.com/microsoft/news/2011/03/hands-on-google-cloud-connect-for-office-not-ready-for-prime-time.ars