Bought My wife one, we have a family pack MM account.
Set her up, no prob.
Set me up, no prob. (can only sync cal, and contacts etc on one account of course.)
Deleted my account via Settings....worked until I went into mail again, FAIL!!!!
Went into mail, my account info was in there. Restarted, all was well again. The mail is not perfect yet, had some hiccups with Exchange server 07 as well.