Some great comments on the "Visual Aspects of Interaction Design" from the Interaction Designers list:
"I would never expect that visual was considered separate, ever. In fact, in the early to mid 1990s, most of us 'interface designers' had to fight the notion that all we did was draw pretty icons." -Andrei Herasimchuk, Adobe
"And while the thought of designers coding their own work might initially sound daunting or perhaps unappealing, it will ultimately be a boon to the profession as designers will finally control the means of production related to their inventions and will therefore be able to exercise additional control, influence, and responsibility in the product creation process." -Bob Baxley, Baxley Design
"Some aspects of visual design are indispensable to an interaction designer (unless one is working with a speech interface). Use of layout grids, alignment, whitespace, visual hierarchy, rhythm and repetition, color, and even elementary typography -these are all fundamental skills for putting together a clear and readable interface." -Jenifer Tidwell, MIT
"I see visual design as much more than aesthetics, however. To me, visual design can provide a gestalt that is as valuable for the cognitive factors as for the aesthetics." -Elizabeth Buie, Computer Sciences Corporation
"If you're talking about aesthetics, that's a different thing and a direction that it might not be best to take this. Good design is a combination of a well thought-out structure and series of interactions, a visual system that engages people and that communicates the nature of the things itself." -Molly Wright Steenson