Since there is no preferred device orientation for iPad, OpenGL rendering on the device must handle that. I have added arbitrary device orientation to my HelloiPadGLSL code to demonstrate how to handle that. It turns out to be relatively easy if you think in terms of the MVC design pattern Apple has established and implement the proper methods in your Controller and View. I include liberal doses of NSLog-ing to stare at for your pleasure:

On GitHub: http://github.com/turner/HelloiPadGLSL

Enjoy,

Doug

twitter: @dugla