A summary of its capabilities are as follows:
1. Power Management - provides a set of tools that enable the site administrator to configure standard Windows power settings across computers. Check out http://technet.microsoft.com/en-us/library/ff977066.aspx for more information.
2. Operating System Deployment - improvements Provides pre-staging of boot images and Windows Imaging Format (.wim) files on new computers that enables the administrator to apply a task sequence to the device that can use the pre-staged media. For more information, check out http://technet.microsoft.com/en-us/library/gg294171.aspx.
3. Dynamic Collection Evaluation - enables you to rapidly evaluate a collection membership by adding only newly discovered resources. Go to http://technet.microsoft.com/en-us/library/ff977097.aspx for more information.
4. Active Directory Delta Discovery - this capability of discovering from AD has been there for a long time. Now it performs an intermediate discovery cycle that adds only new resources to the Configuration Manager 2007 database. For more information, see http://technet.microsoft.com/en-us/library/ff977086.aspx.
5. Simplified Resource Management - Collections are powerful ways to group and manage your objects such as computers and users. This capability enables you to search for and add resources to a specified collection using search strings and variables. For more information, check out http://technet.microsoft.com/en-us/library/ee344335.aspx.
6. Desired Configuration Management enhancement - enables you to create a collection of compliant or noncompliant computers in desired configuration management. Go to http://technet.microsoft.com/en-us/library/bb680546.aspx for more info.
7. Higher Number of Supported Clients Per Hierarchy. In SCCM 2007 R3, it supports up to 300,000 clients per hierarchy when it uses the default settings for all Configuration Manager 2007 features. This increase in supported clients is the result of improvements to the Active Directory synchronization and Collection Evaluation processes.
For downloads, go to the following.
Evaluation version at http://technet.microsoft.com/en-us/evalcenter/bb736730.aspx
SCCM blog at http://blogs.technet.com/b/systemcenter/archive/2010/10/14/configuration-manager-2007-r3-is-here.aspx