As you may already know, with Office 365 you can configure your cloud services to use your own Active Directory for user authentication. This allow single sign on and password policy management independently of Office 365.
However, until now, there was a limitation which obliged you to use multiple ADFS implementation in case of you were using multiple top domain for user’s UPN (user@domain1.com, user@domain2.com…); one per top domain.
With the ADFS 2.0 Update 1, Microsoft has improved this management and now is allowing a single ADFS implementation whatever the number of top domain you are using.
More details http://support.microsoft.com/kb/2607496
More information for ADFS implementation with Office 365 http://onlinehelp.microsoft.com/en-us/office365-enterprises/ff652560.aspx#BKMK_CreateOrConvertADomain