If you are importing VMs created in WS5.x, VMware Server 1.x, or ESX 3.x for use in Fusion that have the virtual USB hardware enabled in them they will not have the ability to take advantage of the new USB 2.0 capabilities by default. If you would like to enable this feature for these VMs open the .vmx file of your VM using text edit and add the following line to the .vmx file while the vm is not powered on.
ehci.present = "TRUE"
if you plan to export the VM back to WS5.x, VMware Server 1.x, or ESX 3.x you will need to remove the line ehci.present = "TRUE" from the vmx file
EHCI support is brand new, and only included in the betas of VMware Fusion and VMware Workstation 6.0 so far.
If you boot a VM with EHCI enabled in an older product, the VM will boot without the virtual EHCI controller connected.
Before release, we will be making changes to the virtual hardware versioning scheme so this is easier for the end user to manage.