I think this would be pretty cool if our default theme used media queries and was able to respond design wise to user agents.
Rather than tailoring disconnected designs to each of an ever-increasing number of web devices, we can treat them as facets of the same experience. We can design for an optimal viewing experience, but embed standards-based technologies into our designs to make them not only more flexible, but more adaptive to the media that renders them. In short, we need to practice responsive web design. http://www.alistapart.com/articles/responsive-web-design/
Marking this as a meta issue for discussion and probably to track resulting issues if we think this a route we can explore.