Sorry prob a newbie question... Is opengl es exactly the same for android and iphone development? X
and (i forgot this 2nd question in first post) ;- is the speed gain with developing games on linux worth all the hassles compared with the convinience of windows? Also since many end users (players) may not necessarily use linux?

Yes. Core part of OpenGL ES is the same - that's the reason why it is called a standard.
Only big difference will how you create context (on Android it is EGL in NativeActivity or GLSurfaceView in Java, but on IOS it will be EAGLContext).
Also expect differences with extensions - you can live without them, but some of them are quite useful. But difference with extensions is because of different GPU vendors. Even on one platform like Androd there is a quite a difference in supported extensions per device.