VMware have just released an update to vCenter 5.1, this update 5.1.0a is just a bug fix release full details of the corrected bugs can be found here
The one that I was happiest to see as I spent a hours trying to rectify recently was as below.
Installing vCenter Single Sign On fails with the error: Unable to create database users: Password validation failed
When you attempt to install vCenter Single Sign On using an existing database or the bundled SQL Express database, the installation fails with the following error:
Error 29114. Cannot connect to DB
This issue is resolved in this release.
I was glad to read this was a bug as I was pulling my hair out for a while whilst trying to instal sso for an internal upgrade I was doing. If anyone does have problems I also found the resource below very useful