A. If you plan to upgrade to Exchange 2010, the answer is no. Microsoft has changed your mailbox high availability options for Exchange 2010—there's a single high availability model based around database availability groups (DAGs). DAGs can be thought of as a combination of cluster continuous replication (CCR) and standby continuous replication (SCR). There's no equivalent of single copy cluster or local continuous replication in Exchange 2010, so if you're designing an Exchange 2007 architecture that follows today's best practices and prepares for the future, stick to CCR and SCR.
Related Reading:
Check out hundreds more useful Q&As like this in John Savill's FAQ for Windows. Also, watch instructional videos made by John at ITTV.net.