Login VSI is really the only company out there that effectively performs load testing on a VDI infrastructure.
More information on Login VSI can be found at http://www.loginvsi.com.
Login VSI was a bit difficult to use in the early versions, but they tout that the latest versions are easier to use than before. If you have ever read a performance report about Virtual Desktop Infrastructure, then Login VSI was likely the basis for that testing. If you are implementing a small-to-medium deployment of VDI, the risk of finding and mitigating performance issues is the same as it would be for a large deployment.
The reality is, no matter how much time and preparation you put into making sure your solution is built for performance, there ...