I'd like to get some clarification regarding compatability.
In particular, upgrading servers from ESX 4.0 to ESXi 4.1.U1.
Are there any compatability issues with the above upgrade relative to:
We're wanting to ensure that what we have isn't going to go pear shaped after we start down the upgrade path and lose the ability to use any of the above.
Direct Upgrade the system from ESX to ESXi is not supported. you have to follow the migration steps http://www.vmware.com/products/vsphere/esxi-and-esx/
All the functionlality that you have listed will work perfectly in ESXi4.1U1 as well. Make sure that you followed above procedure. Also make sure that you upgrade the vCenter Server and Update manager to 4.1U1 before you start ESX migration to ESXi.