We have a Dell Poweredge server running ESXi 4.1 U1 that was installed using Dell's customized ESXi ISO. Now we would like to upgrade to 4.1 U2 and upgrade any Dell specific bits that were installed.
I downloaded the 4.1 U2 Dell Customized ISO and tried to install over the existing installation but it doesn't look like I can do that non-destructively.
I tried upgrading using VMware's Update Manager, and that upgrades the ESXi installation, but I don't think it upgrades the Dell specific bits.
As far as the Dell management components are concerned, you should be able to add the Dell OpenManage Offline Bundle and VIB for ESXi to the Update Manager Patch Repository as a Host Extension, create a baseline for Host Extensions, attach the baseline to your host, scan the host for patches and upgrades, and use Update Manager to install/update the OpenManage bundle.
I believe the latest version of OpenManage for ESXi4 is 6.5.
http://www.dell.com/support/drivers/us/en/04/DriverDetails?driverId=R300511&fileId=2731126594
The Dell specific bits are really just CIM and SNMP providers. You can use update manager to update this installation. If you choose to do something like upgrade to 5.0, then you should use a Dell ISO.
Run update manager as normal. Dell specifics are probably similar to HP's, and are independent of the ESXi installation. I'll often take an HP custom ISO and update it via update manager. The HP agents/utilities remain unchanged.
You should also be able to update the Dell bits independently as well. Look for a Dell "offline bundle" containing the CIM package.