ios and onGUi performance / alternatives?

I recently saw online that for ios development that in unity3d the function onGUI should be generally avoided because it can/will significantly increase draw calls and can adversly impact performance. My question has 2 parts:

1 for people who have developed for ios, has this been your experience? and

2 what alternatives are there for creating a GUI for ios unity applications (I mean from within unity and not really doing a GUI with native objc)?
As someone new to unity, any advice would be greatly appreciated.

Cheers Chris

Most people use the legacy GUI stuff in iOS development, like GUITexture, GUIText.