I've been deploying vCenter as a virtual server since about vSphere 4, prior to that I liked to have it as a physical server because I didn't like the idea of the management server sitting inside what it was managing. I have not had an issue with running it as a virtual server on the cluster it is managing.
I simply rely on VMware vSphere HA for handing resilience.
If you are not on vSphere 5.5 update 2 then I suggest NOT upgrading the hardware version of your vCenter server to 10 as you will only be able to edit the settings of the VM using the vSphere Web Client and if the vCenter server is down then you cannot use the vSphere Web Client! From vSphere 5.5 Update 2 you can edit a HW v10 VM using the C# client.
If you have a large infrastructure then you could consider implementing a "Management Cluster". This could be a cluster containing just two hosts and run things such as vCenter, SQL server for vCenter, Windows Active Directory Domain Controllers, DNS, DHCP, vCenter Operations Manager, vMA, e.t.c.