In addition to the app's launch, Steam has also officially announced that Link is compatible with Xbox 360 wired and wireless, Xbox One wired and Logitech F510/F710 controllers in addition to its own gamepad. Testers were actually able to use those controllers with the app during the beta period, which is why Steam knows rumble on Xbox controllers causes a lag spike. The Link team is trying to find a way to fix that and will likely include it in future update, along with any other patches and new features.