The increasingly joint nature of operations with the Department of Defense and the expanded use of the most senior warrant officers in joint operations validated the need to standardize CW5 rank insignia among all the services that employ them. The effective date for wear of the new CW5 insignia and branch-specific insignia and colors was 9 July 2004 to coincide with the 86th anniversary of the Warrant Officer Corps.

See the new insignia here:
http://www.military-ranks.com/army-ranks.htm

well, i think the new insigna looks better than the old one

It's similar to the Navy and Marines W5s now
(No Warrant officers in the Air Force...)