Our organization recently began deploying approximately 100 or so Microsoft Surface Pro. devices to users. One of the first groups to connect with it to XenDesktop noticed that the stylus, type cover (keyboard) and touchpad did not work. After acquiring a test unit the cause became clear right away: Upon connection, the interface devices were being redirected to the VM itself, taking them away from the surface itself. I searched a bit for drivers which I could load into my image, but ultimately I decided on disabling USB redirection for this one device.
DENY:VID=045E PID=079C #Surface USB Composite Device
Adding this line to “Client USB Redirection Rules” will prevent the devices from being sent to the virtual session. Citrix Receiver is then responsible for sending input from the host (which now functions as expected) and your users can use the stylus, keyboard, or touchpad as they would expect.