I would love a metric units feature. It'd stop me from having to go online all the time to find out how many kilometers, etc, my character can jump and so on.
Wizard's published something on their website about Going Metric a while back, which includes information on how the conversion was done using existing rules (eg: the Star Wars RPG).
Here's the links:
Part 1:
http://www.wizards.com/default.asp?x=dnd/rg/20040316a
Part 2:
http://www.wizards.com/default.asp?x=dnd/rg/20040323a
Part 3:
http://www.wizards.com/default.asp?x=dnd/rg/20040330a
Part 4:
http://www.wizards.com/default.asp?x=dnd/rg/20040406a