Recently I received my MacBook Pro. It’s the 13″ model with Retina Display. I run it in the 1680×1050 HiDPI mode to get more content on the screen (I use the nice little tool called QuickRes to conveniently switch resolutions).
Before I had the MacBook Pro I was working on a MacBook Air with significantly lower resolution and when testing my iOS apps in the Simulator, I had to scale the Simulator down to fit on my screen. This can easily be done by pressing CMD+1 (100%), CMD+2 (75%) and CMD+3 (50%) or via the Window -> Scale options.
Now with the MacBook Pro it is the other way round: an iPhone 5 is simply too small even at 100%. See the screenshot below.