Earlier this year i have found two errors within the Get-DistributedSwitchPortGroup cmdlet from the book “The VMware vSphere PowerCLI Reference: Automating vSphere Administration”. The book is a great resource for automating vSphere environments and the scripts extend PowerCLI with the missing dvSwitch cmdlets and other useful stuff.
With the vCenter Update Manager you cannot remove installed packages. For ESX5i one option is to use a few commandline steps in the local ESX shell.
Logon to ESX Host with SSH query the package name: esxcli software vib list |grep -i emc