Yes! This is important. I get really worked up when I see basic concepts of design ignored by developers. I mean, I’m not a great designer by any means, but we can all learn a few things.
Here are some excellent tips for getting started, by Mel Choyce on ThemeShaper.
Related, as Sarah Gooding reports, design guidelines have also been added to the theme handbook. My hometown designers are representing in the related resource section (both whom I’ve worked with): Sara Cannon and David Hickox. Two of the best around.