Whenever a new service pack is released, it is typically like a grab bag of features that may or may not be applicable to your environment -- but you are happy to see them nonetheless. Service Pack 1 for Exchange 2013 (also known as Cumulative Update 4) follows this pattern.
Let's take a look at the major new features in Exchange 2013 SP1.
Windows Server 2012 R2 support: It's obviously nice to be able to install the latest version of Exchange on the latest version of Windows Server. Keep in mind: If you already have Exchange installed on Windows Server 2012, you cannot upgrade to Windows Server 2012 R2; you need to do a new install in that case.
Edge Transport 2013 has arrived: The Edge Transport role sits in the perimeter (or DMZ) and handles all Internet-facing mail flow, provides additional security through agents and transport rules, and in the process, reduces the attack surface. I'm not a huge fan of the Edge Transport role -- I prefer cloud-based or appliance-based alternative -- but I found it oddly absent in the original release of Exchange 2013. One note of caution regarding the Exchange 2013 SP1 Edge Transport role: You have to configure it through PowerShell in the Exchange Management Shell.
Exchange MVP Tony Redmond says, "Some will decry the lack of a GUI and the need to manage the server with PowerShell, but the tasks to set up an Edge server are relatively straightforward. And anyway, if you can't handle a few PowerShell commands, maybe you should not be setting up a server that acts as the secure inbound email access point for the organization." It's rare that I disagree with Redmond, but in this case I believe a system that will be primarily a set-and-forget type of server shouldn't be made more complicated by the lack of a simple GUI. If the tasks are "relatively straightforward," it should have been easy to give admins a GUI to keep it simple. Let admins focus on more pertinent matters. I suspect that due to the lack of a GUI, admins won't use Edge Transport and instead will go with alternative protection.