Here is a link to Dan Holme's articles on his experiences with Microsoft Online Services.
The report card: "Final Report: "A" for Effort & Service; "A-/B+" for Features – Absolutely Worth ExploringWhat Microsoft has attained in this first release is an extraordinary, robust, enterprise-ready service. I don’t expect there to be many fundamental problems (security, reliability, availability, performance) based on my experience thus far. ":http://www.officesharepointpro.com/TabId/149/NodeId/1950/a-microsoft-online-report-card.aspx
His migration experiences: http://www.officesharepointpro.com/TabId/149/NodeId/1951/my-migration-to-microsoft-online.aspx