I have just completed an 80 mailbox migration from Cloudmore to Micrososft's BPOS Standard suite.
I had only done a 5 user BPOS site prior to completing the 80 user site. And got stuck in over the weekend and began migrating.
Microsoft do provide a lot of excellent templates to obtain user names and to help plan and structure the migration which I didnt use but will do in future as I can see how beneficial these templates are.
A couple of points to note.
Dont forget to register your Microsoft Partner ID in the customer portal.
The AD Sync tool is no use if there is no exchange information in AD , Like email addresses etc..
The Microsoft Migration Tool works really well but there is a lot of powershell for making custom changes.
I have put Google Apps in for a few customers in the past but BPOS wipes the floor with Google Apps. The functionality is amazing Sharepoint, OCS, Live Meeting, Outlook Anywhere, OWA, Seamless integration with smartphones, 25gb storage per user!!
Some of my friends working in IT services mentioned that we will all be out of a job with everything up in the cloud and Microsoft even have radio advertisements saying " Hassle free IT" But it can be quite tricky to set up and fairly tricky for customization.So I think our jobs are safe for now.
I also found submitting service requests via the BPOS Admin Center or contacting Microsoft Online Support to be very helpful.The Microsoft Support team was always very friendly and really quick at resolving issues.
Finally I deployed the OCS Client and BPOS Sign in Application via SCE2010 which is just so easy!!