Here's the clip from the show. It doesn't really show much, but some very good super fans noticed something that might be rolled out in the next title update; experience for Horde. Take a look at the 2'49" when it shows a new wave starting. The bottome right hand corner has a pop-up showing "Experience Gained" from the previous wave.
Gears of War 2: All Fronts Expansion Pack Preview Videos - G4tv.com
Edit - I found a post over on the Epic forums by joeGraf that confirms they will be adding XP to Horde.
Edit 2 - It also looks like they are considering removing the stun and rag doll result from smoke grenades. It may be replaced with the "cringe" effect often seen from friendly mortar fire. Or removed completely...
Gears of War 2: All Fronts Expansion Pack Preview Videos - G4tv.com
Edit - I found a post over on the Epic forums by joeGraf that confirms they will be adding XP to Horde.
Edit 2 - It also looks like they are considering removing the stun and rag doll result from smoke grenades. It may be replaced with the "cringe" effect often seen from friendly mortar fire. Or removed completely...