The Alfred blog:
Alfred v2 is re-written from the ground up to be faster, more efficient and easier to use. Overall, less than 15% of Alfred v1′s code was reused, and every feature was carefully improved and given the love it needs.
Some of the highlights of v2 include the new Workflows framework, which we sneak peeked for you during the beta and replaces the Extensions from v1. Alfred users have created amazing workflows, some of which you can find on the new Alfred forum.
Worth every penny. Such an absolutely fantastic app, now with boatloads of new features.