That battery is an excellent choice for the camera. It's not very big or heavy, but it'll last around six hours.
The DVXUSER.com battery is a much better buy considering dollars vs. capacity, but the D54 is the longest-lasting battery you can get, so for convenience it's a great choice.
Like Barry said, it's cool because it last a long time and balances the camera well, but you can buy much more juice for the same money with the DVXuser.com batteries. ;D