Preview and simulate are not the same
On the main work area, the text looks tiny even though it's 12 pt font. On preview, it is also tiny. But on simulate, it is the correct size.
Also, the font of the tab names is tiny. And the font of 'publish online' and 'simulate' is tiny.
I'm on a Macbook Pro Retina if that matters. And btw, I see that you fixed the retina icon problem in version 5, I appreciate that.
edit: I should note that this problem did not exist on the 4.x version on the Retina. I just upgraded today and saw it.