The Exchange Team Blog has published 2 nice articles about the new Exchange architecture:
http://blogs.technet.com/b/exchange/archive/2013/01/25/exchange-2013-client-access-server-role.aspx
and
http://blogs.technet.com/b/exchange/archive/2013/01/23/exchange-2013-server-role-architecture.aspx
I think both articles are well worth reading. Currently the SP3 for Exchange 2010 is eagerly awaited so that the migrations can finally start. Unfortunately, there is still no news on when the service pack will be released. The date is still the first quarter of 2013.
The time until the release can be used to take a closer look at Exchange 2013, even if probably only a few will be using it in productive environments so far.
My test environment for the migration is already ready, so I'm eagerly awaiting the release.
