If you make your way to have a look at the full release notes from ATI, you see performance fixes and a massive list of bug fixes for some very popular games.
If you're having trouble with your current set of drivers, it's worth the upgrade but if you're not having any troubles and you still find yourself playing OpenGL games you are better off sticking with your current Catalyst 6.3 drivers.
Big performance was seen last year in the two December releases so we have no doubt that ATI are more concentrated on fixing gaming problems at the moment. We don't doubt though that we will see a performance increase in the driver set in the coming months.
Until next month, have a great Easter and Happy Benchmarking!