So, it looks like guild talents are no longer "optional". You won't spec your guild as fit, you will earn rewards as your guild levels up. Mounts w/ TabardBanners.. Heirlooms, etc.

http://www.wow.com/2010/06/13/catacl...ency-scrapped/

Raid Lockouts are becoming more forgiving, and there will be more Algalon style encounters unlockable only by defeating the final boss on hard mode.

http://www.wow.com/2010/06/13/catacl...ics-announced/

Minor Cata Lore information
http://www.wow.com/2010/06/13/catacl...ails-revealed/

Overall information
http://www.wow.com/2010/06/13/catacl...nsion-details/