You need to bear in mind that the screen resolutions of android devices vary widely which may affect the way you develop your GUI - also all mobile platforms are lower power than desktop ones so you should choose shaders for performance and try to keep materials and textures atlased so that dynamic batching will reduce your draw calls (minimising scaling is also important for this I believe).

Mobile platforms use touch to simulate the mouse - but this does not extend to OnMouseXXX methods - there is a script which simulates this behaviour too, but it is an add on.

You should also not rely on being able to compile code at run time so methods that cause the compiler to emit custom code at run time should also be avoided (these can be a little hard to spot). If you are doing no reflection then this should not be a problem.