There is no one size fits all solution for load balancing CAS arrays. You may find that simple Windows Load Balancing will work for you, or you may have a need for bigger (and more expensive) hardware load balancers. Do your research. Learn. Become an expert.
I encourage you to read Exploring Exchange 2010 RPC Client Access Service on the MSExchangeTeam blog. This article gives an excellent overview of the new RPC Client Access and Address Book services in Exchange 2010. It also explains many of the details about Client Access arrays. 1:21 PM