Service Pack 2 (SP2) for Windows Vista and for Windows Server 2008 supports new kinds of hardware and emerging hardware standards. This service pack includes all the updates that have been delivered since Service Pack 1, and it simplifies deployment for consumers, for developers, and for IT professionals.- Microsoft Site
Basically the server side component helps in deployment of on going updates by working with software and hardware distributors; as well as, help Admins deploy and manage large installations. Both updates are focused on emerging hardware standards. Enterprise improvements consist of Hyper-V virt enviro, better power management via group policy, and WebDAV compatibility. It is also a single installation package so just one for both Vista and Server, so makes pushing it out a breeze.