Do you Need to run Exchange 2010 preps in Account Forest?

Hello,

In Exchange 2003 days, you had to run Forest Prep, and you had to run Domain preparations on any domain of that forest that was going to contain user objects with mailboxes.

In Exchange 2010, if one were to create from scratch (no previous Exchange) an Account Forest and an Exchange Resource Forest, Is it required to run Exchange 2010 Forest or Domain Prep on the Account Forest?  

Follow up question, what if the Account Forest mentioned in the above question is an existing Forest that has user objects with mailboxes on an Exchange 2003 Server in the same forest.  Would Exch 2010 preparations need to be run, and what of the impact on the current Exchange 2003 users and mailboxes? (regarding the need for /PrepareLegacyExchangePermissions or anything)

References (that don't answer the above for me):

Deploy Exchange 2010 in an Exchange Resource Forest Topology
http://technet.microsoft.com/en-us/library/aa998031.aspx

Prepare Active Directory and Domains
http://technet.microsoft.com/en-us/library/bb125224.aspx

Thanks in advance