Here is a link to the product page: http://www.shunra.com/vedesktop.aspx

We do a lot of this kind of testing and opted for the Shunra VE appliance. You have a lot more control, a lot more options, and lot more reporting which is required if you need to do this on a bigger scale. With a couple of VLANs on your ESX host(s) and the VE appliance setup in router mode this is pretty easy to do.

We do use the desktop product as well for some small testing done by developers working on a specific fix/feature.

Hope that helps!