Do you know of any good examples of CSS-based layouts using units like inches or centimeters?
When I do mobile web, I use percentages for UI layout elements (like headers, footers, sidebars, etc), and pixels for text, buttons, etc.
This approach definitely results in a slightly different display on different screen resolutions, but the overall effect is that it looks good and is usable no matter where you view it. For me, this is the approach I've found that "just works", so I keep using it.
That said, I don't think I've ever seen centimeters and inches used in any CSS I've come across, but I'd love to see some examples that are well done.