With the General Availability of the vSphere 5.1 release i wanted to share what that means for vCenter Server 5.1. Some of the highlights of this release are:
The vSphere Web Client: 
Our new, full featured Web Client, provides a platform independent administrative UI.  The browser based client is now the primary client for vSphere administrators in vSphere 5.1.  The vSphere Web Client is built around improved a consistent usability experience, concurrent session performance and designed to scale for an increased number of administrators.  As the new administrative face of the Cloud Infrastructure Suite, the Web Client also offers a rich set of integration points that allows other VMware solutions and 3rd party solutions to integrate seamlessly into one single pane of glass for all VMware administrators.
Ability to view multiple vCenters on the same vSphere Web Client without the need for Linked mode. Search capabilities across all these vCenter instances. Now you can find your VM from thousands spread across multiple vCenter instances. 
vCenter Single Sign On Service:
This newly introduced service enables support for authentication against multiple identity sources at the same time, including Active Directory (AD) and OpenLDAP. Multiple AD domains can be connected to vCenter Sign Sign On. vCenter now supports open identity standards such as SAML 2.0 and WS-TRUST. This also enables Single Sign On between vCloud Director Admin user interface and vSphere Web Client. 
vCenter Inventory Tagging:
vCenter now supports Tagging of its inventory. Tags can be created and assigned to one or more vCenter objects as a grouping mechanism. Objects can be searched using tags as well. If you had always wanted to place the same VM in multiple folders, you can now tag the same VM with multiple tags as a way to organize these VMs any way you want. 
vCenter Performance Optimizations:
Significant performance improvements have been achieved, for example in the area of vCenter’s statistical data. No matter how large your environment is you will no longer encounter performance issues creating, rolling or purging stats, no matter which stats level you choose to use. Stats get rolled up in minutes as opposed to hours irrespective of the granularity or level of rollups. Improvements in database improves the overall performance of vCenter. 
Some useful links: 
Release Notes: 
Download Landing Page: 
Documentation Landing Page: 

Overview Videos: