vCenter Server has become a mission critical part of most virtual infrastructures. It can be a single point of failure if it is not designed for availability. vCenter Server 6 has many changes relating to vCenter Server and its components and careful consideration has to be made in the design of its architecture.
There are multiple solutions for high availability. Many of these options can be combined to provide different levels of availability. vSphere HA, FT, vCenter Watchdog services and in guest clustering solutions can be combined depending on customer requirements for availability.
The Platform Services Controller (PSC) serves many VMware solutions in addition to vCenter Server such as VROPS, View, etc. The PSC deployment modes have to be carefully evaluated based on unique customer requirements and architected appropriately as well.
The VMware vCenter Server 6.0 Availability Guide is a great resource for architecting a HA solution for vCenter Server. I hope you find it useful!