We recently made a presentation at the Qt Developer Days conference in San Francisco, entitled Make Your Content Shine: Design Choices for a Qt Touch Kiosk.
When installing a touchscreen kiosk, the angle of the screen is a major consideration. First, it affects how quickly people perceive the device as interactive and also touch-enabled. (See my previous post, Is That a Kiosk? How to Best Position Your Public Touchscreen Display for Use.) Second, it affects how comfortable it is for users to perform touch gestures.