I discovered that my drawRect is being called more than once. Unfortunately this had the unfortunate side-effect of double-drawing everything because all my subviews are drawn in drawRect (I'm s strict atheist w.r.t. Interface Builder).
What is the best way to deal with a multiple calls to drawrect? A flag to check if it's being called again? Or clear the whole view and redraw from scratch (as I have done?)
When UIKit calls drawRect:, the graphics context set up to draw into should already be cleared for you (unless you have set the clearsContextBeforeDrawing property to NO). Are you perhaps calling drawRect: manually instead of calling setNeedsDisplay/setNeedsDisplayInRect:?
Also, each view is responsible for drawing only its own content and not the content of its subviews.
What do you mean by "your subviews are drawn in drawRect"? If you mean that you're putting calls to -addSubview: in your drawRect, don't. Move those to a more appropriate place that gets called only when it needs to (probably the -initWithFrame: method for your view if the subviews are always there), and use drawRect only to do custom drawing.
Strictly speaking, being called multiple times is the entire point of -drawRect. It's called to update small parts of your view when needed. It's actually called quite often if you're updating your view (moving it around, updating the superview, etc.), so it should be as simple and fast as possible to avoid performance problems.