Thank you for the informative article. My experience suggests that this feature is a "nice to have" feature.
With the even heavier reliance on CAS servers under 2010, please pleASE PLEASE make sure that client redirection and load balancing are BULLETPROOF. I'd much prefer to explain why "delivery reports" is flakey than to have the whole conversation (for example, about the Exchange 2007 issue with client redirection when CAS and MB are on the same server; I could keep going on and on here) about the problem with some clients and shared role servers.
Simply said, please make sure the important stuff "just works" instead of cramming "nice to have" features into the product.