Well I'm looking forward to it...
If it helps - this is the complete script I ended up using ...
Add-PSSnapin VMware.VIMAutomation.Core
$vcserver = "vcenterserver"
$vcusername = "username"
$vcpassword = "password"
$myhost = "Host that USB is attached to"
$myvm = "VM which to pass USB through to"
$pid = "PID of USB Device"
$vid = "VID of USB Device"
Connect-VIserver $vcserver -user $vcusername -pass $vcpassword
#get id of VM
$vm = get-vm $myvm
$vmid = $vm.ID
#get host uuid from BIOS
$vmhost = get-vmhost $myhost
$vmhostId = $vmhost.ExtensionData.Hardware.SystemInfo.Uuid
#reformat vmhostID to the proper format for autoconnect string
$vmhostd = $vmhostid.Replace("-","")
$section1 = $vmhostid.substring(0,16)
$section2 = $vmhostid.substring(16)
$newsec1 = (&{for ($i = 0;$i -lt $section1.length;$i += 2) { $section1.substring($i,2) }}) -join '\ '
$newsec2 = (&{for ($i = 0;$i -lt $section2.length;$i += 2) { $section2.substring($i,2) }}) -join '\ '
$hostId = "$newsec1-$newsec2"
#create usb device and add it to the VM.
$spec = New-Object VMware.Vim.VirtualMachineConfigSpec
$spec.deviceChange = New-Object VMware.Vim.VirtualDeviceConfigSpec[] (1)
$spec.deviceChange[0] = New-Object VMware.Vim.VirtualDeviceConfigSpec
$spec.deviceChange[0].operation = "add"
$spec.deviceChange[0].device = New-Object VMware.Vim.VirtualUSB
$spec.deviceChange[0].device.key = -100
$spec.deviceChange[0].device.backing = New-Object VMware.Vim.VirtualUSBUSBBackingInfo
$spec.deviceChange[0].device.backing.deviceName = "pid:$pid vid:$vid hostId:$hostId"
$spec.deviceChange[0].device.connectable = New-Object VMware.Vim.VirtualDeviceConnectInfo
$spec.deviceChange[0].device.connectable.startConnected = $true
$spec.deviceChange[0].device.connectable.allowGuestControl = $false
$spec.deviceChange[0].device.connectable.connected = $true
$spec.deviceChange[0].device.connected = $false
$_this = Get-View -Id "$vmid"
$_this.ReconfigVM_Task($spec)