I have been riding these for quite a while now:

http://www.ritcheylogic.com/dyn_prodfamily.php?k=98031

There is a weight penalty with most of these bars but I will never go back to round bars. At 6'4" I have large hands and was never comfortable on long rides with a round bar. I also find them to be excellent for climbing. I suspect I will switch when these become available:

http://zipp.com/bars/vukasprint/

They are lighter and I expect up to Zipp's usual level of super stiff and strong.