I work with several small business which have their own Exchange servers (2007 and 2010) on prem. Most of these companies have less than 20 users. I'm looking for best practices in moving these companies to Office 365 or other Exchange hosting solutions. Many of them are law firms or accounting firms. Multi user calendars are very important. In the early days of Exchange hosting, many just offered an OWA experience. How is the full Outlook experience? Other than moving the mailboxes, changing the MX records, what are the other major hurdles?