UPDATE: On Sep 18th Cisco released 2.0(4a), which you can download from Cisco support.
For those of you that are Cisco UCS customers, word on the street is that a forthcoming firmware update 2.0(4) will be required for official vSphere 5.1 support. Cisco should have the updated firmware out by the end of September or early October. As for a Cisco UCS customized ESXi 5.1 installation media, that may be towards the end of October.
Hi Derek, do you have any news on the customized installation media ?
Update.
I found that VMware has uploaded “ESXi-5.1.0-799733-custom-Cisco-2.1.0.3.iso”.