As much as everyone thinks this runway will help a lot with delays and congestion, most of those issues went away when 27R was opened.

This runway was designed specifically for the Class VI aircraft (A380, 748) and currently the A380 is not authorized to operate to ORD yet. All the 748 operators are cargo and can use other runways but are restricted to taxiing outside the main terminal complex due to wingtip issues.

What will help is when the 3rd southern FAA tower is built. Then you can start looking at ORD as two separate airports. The Northern which will cover UA and the Southern which will cover AA. The Center FAA tower will handle clearance delivery, clearance and both inbound and outbound traffic.

There's some proposed taxiway construction planned for 2013 which will make some quality of life improvements near T5.