Interestingly, most the themes I tried didn't render well on my screen. Elements clipping or rendering on top of each other in funny ways, stuff like that - all the typical stuff that happens when the designer didn't consider how the page might render on a smaller screen than the one they have.

I'm rocking a 13" MacBook with the browser in full screen mode, so I suspect my screen's dimensions are well within the range of typical users. The fact that I encounter sites like this on a daily basis is an eternal source of wonder.