I recently had a conversation with a friend about the design of an installer application. I pointed out that its visual flow was confusing. It led my eyes from the left to the right and then up to the top and then back down to the bottom left and finally across to the right. He responded that he doesn't think visual flow is especially important to graphic design. Does having a clear direction and flow between elements matter in graphic design or is unimportant compared to other aspects?
The visual flow of an interface does matter, and here's why:
One of the best resources I've seen on this topic is a video series by StomperNet (ignore the sales pitch, the videos are worth putting up with it). The focus of the videos is to improve website conversions, but there are a lot of solid design principles with a scientific basis in them that could be applied to any design.
If video isn't your thing, check out this study, Identifying Web Usability Problems from Eye-Tracking Data (pdf), which highlights specific usability problems that stem from a poor visual flow.