If the reason you have not been using VSO was concern over where it is hosted, then last week Microsoft made an announcement that could ease some of your worries, or at least your legal departments. VSO now has ISO 27001 Certification and European Model Clauses; for more details see Brian Harry’s blog.
This added to the fact that since the end of last October you have been able to choose to host your VSO instance in Europe could well make VSO a more compelling option for many organisations who don’t want to have their own TFS servers on premises