I just switched to an Easton EC90 Aero from a regular bar:

http://www.eastoncycling.com/en-us/r.../ec90-aero-303

and I enjoy it. I have larger hands so the extra real estate ontop makes for a more comfortable ride. I haven't felt any kind of performance boost while climbing, but extended climbs are noticeably more comfortable. I had a 15 mile...4200 ft climb, a real hamstring punisher,and basically spent an hour up top; nothing went numb.

Also, I put an alum stem ontop for a little more flex...those wing bars are really stiff.