A few months ago I blogged about how to create your own custom Cisco UCS ESXi 5 U1 installation media, with the latest security patches and drivers. There was also an ISO image on VMware’s web site, which magically disappeared for a while. Well, now it appears to be back. There is a Cisco Custom Image for ESXi 5.0 U1 GA Install CD dated 8/28/2012. You can download it here, under OEM Customized Installer CDs. At as of April 2013 Cisco has not released an ESXi 5.0 U2 custom install ISO. So use the 5.0 U1 ISO for the time being.
Unfortunately the Cisco release notes PDF hasn’t been updated since April 2012, so without deconstructing the ISO image I have no idea what is updated. But as always, I would use the latest ISO when deploying new UCS servers.