title: What is the impact of view.alpha = 0 vs view.hidden = YES?
body: <p>Transparency is evil, on iOS devices even more so than on heavier machines. I therefore figured to use <code>view removeFromSuperView</code> first, if not applicable <code>view.hidden=YES</code> and as a last resort <code>view.alpha=0</code>. But I actually don't know what's going on behind the scenes. Is there a difference, especially between the latter two?</p>
  
  <p>I have a <code>UIView animateWithDuration:animations:completion:</code> scenario, where if you put hidden=YES in the completion block, it will hide without letting the animation block finish. Therefore I have to resort to alpha=0.</p>
  
  <p>What are the penalties of the one over the other?
  Cheers, EP.</p>