In this work we evaluated the usability of tangible user interaction for traditional desktop augmented reality environments. More specifically, we compared physical sliders and tracked paddles, and traditional mouse input for a system control task. While task accuracy was the same for all interfaces, mouse input performed the fastest and input with a tracked paddle the slowest. Performance with the physical sliders fell between those two. We present these results along with various findings from user comments, and discuss how they may influence the design of future desktop AR systems.