A ConfigMgr 2007 hierarchy could support a maximum of 200,000 clients (300,000 with R3). ConfigMgr 2012 supports up to 400,000 clients in a Single Site hierarchy when the database for the Central Administration Site is running SQL Server Enterprise. Each Primary Site can support up to 100,000 clients if the database and Primary Site roles are hosted on separate servers.
As with ConfigMgr 2007, each Management Point (MP) can support up to 25,000 clients. However, the concept of a Default Management Point no longer exists in ConfigMgr 2012, and neither does support (or necessity) for Network Load Balancing (NLB) an MP. Instead, up to four servers can host the MP role and clients manage the load balancing in much the same way as they do with Distribution Points.
ConfigMgr 2012 also increases the number of supported Distribution Points (DPs) per site from 100 to 250, each supporting up to 4,000 clients. As the PXE Service is now a feature of the DP role, it is no longer constrained to 75 per primary site as recommended in ConfigMgr 2007, although no specific recommendations for the maximum number of PXE servers per ConfigMgr 2012 site or hierarchy have been provided by Microsoft as yet.