I have to be honest, we have been attempting to migrate 10 users from exchange 2010 without success (off and on for about two months). The tool will migrate small mailboxes, ie under 300MB or so (not sure of the exact size, but not large mailboxes for sure), but you get into multiple GB and it does not work at all. In fact, I cannot ever tell if it does anything.
There should be some UI feedback that indicates that the migrations are X% complete. Or anything. I cannot find any error logs to show why it is not working (even though it will tell you there are migrations in process.) I am really really frustrated. For all the good things that smarter tools has, migration is a really weak point and for those of us acquiring new companies it's a mission critical piece that should be developed as one. Just my .02 cents for anyone else out there that may not be able to get it to work. And before you respond with other methods such as imap... That is not a no touch migration like our users and owners expect.