It looks like there's a problem with the SDK, where fonts appear to be lower-resolution than they ought to be.
On the left, it shows the Corona Simulator with a grey button and a text object sitting on top of it.
On the right, I have a mock-up for my app loaded in Fireworks with the same thing -- a grey button and a text object on top of it. (I exported the grey button image for use my app, but wanted to use Corona's built-in features to generate the text for the buttons.)
As you can see, the resolution of the font seems really low. Anyone have any idea why this might be?