VMware releases Update 5 for VirtualCenter 2.5
More information @ VMware Support website >> http://www.vmware.com/support/vi3/doc/vi3_vc25u5_rel_notes.html
New: Support for High Consolidation in VMware HA Clusters – VirtualCenter 2.5 Update 5 includes significant performance and scalability improvements to VMware HA. Use VirtualCenter 2.5 Update 5 for environments with more than 35 virtual machines per host in an HA cluster.
For information on the ESX Server host settings required for this scalability improvement, see ESX Server host settings required for environments with up to 80 virtual machines per host in an HA Cluster (KB 1012002).