Data and information visualization has been a source of stimulating design challenges (and jobs, for that matter). I've done a handful of projects as part of two data visualization classes and two research intern positions. With such vital examinations of scale, complexity, hierarchy, summary, human vision, and information processing, I've found that visualization is an essential field of study.
Visualization research has yielded principles for so many subject, such as animation, color, saliency, that easily improve any visual presentation. Hence, my study and work in visualization is a constant influence on the way I design interfaces and interactions.