DCurrie,
I am in the same boat as you. I have all HP hosts DL380s. I migrated my test hosts to my vCenter 5.5 U1 server, and went to perform the upgrade on the hosts from 5.1. I first had to apply the latest patches on 5.1, which then allowed me to upgrade the host to 5.5.0. I then had another series of patches that I applied (assuming I had to do that before upgrading to 5.5.1). After applying those, I still have 5.5.1 as an incompatible upgrade.
The upgrade contains the following set of conflicting VIBs:
Broadcom_bootbank_net-bnx2_2.2.5dv55.2-1OEM.550.0.0.1331820
Remove the conflicting VIBs or use Image Builder.....
So, I was at least able to make it to 5.5.0, but no further. Both the 5.5.0 and 5.5.1 ISOs used are the HP OEM ISOs.
I have bnx2_2.2.4f.v55.3 currently installed.
HP has bnx2_2.2.3t.v55.7 as downloadable under the vSphere 5.5 section.
VMware under the HCL has multiple versions including my current version and the bnx2_2.2.5d.v55.2.
Since this is test, I will play around with it some more and see what I can figure out.
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Update: From Release Notes of 5.5 U1b
Update Manager reports the compliance status as Incompatible when scanning or remediating ESXi 5.x hosts that belong to an HA cluster
When you perform an upgrade scan of ESXi 5.x hosts that belong to an HA cluster, Update Manager might report the compliance status of the hosts as Incompatible and might not allow the hosts to be remediated. The Incompatible compliance status is because of the way the FDM (HA) agent is installed on ESXi 5.x hosts. Starting with vSphere 5.0, the FDM agent is installed on ESXi hosts as a VIB. When a VIB is installed or updated on an ESXi host, a flag is set to signify that the bootbank on the host has been updated. Update Manager checks for this flag while performing an upgrade scan or remediation and requires this flag to be cleared before upgrading a host. The flag can be cleared by rebooting the host.
Workaround: Reboot hosts that report the compliance status as Incompatible. Run the upgrade scan or remediation again after the host is back online.
Going to give this a try and I will let you know how it goes.