A panel at E3 spat out all kinds of Gears of War 2 tidbits. The most revealing were than there is a possibility of a $130 GoW2 Bundle that ships with a miniature Lancer and the "Linked Achievements" precedent. Here's IGN's list:

# Gears 2 will use what's being called Linked Achievements. Players who played Gears 1 and completed Act 1 will be able to play as Carmine in Gears 2's multiplayer. If you killed Raam at the end of Gears 1 his character model will be available as well. There will be more Linked Achievements in Gears 2, but those were the only examples given.
# Steve Jablonsky recently finished the last recording session at Skywalker Sound for the soundtrack. He also did Transformers and the remake of Texas Chainsaw Massacre.
# You'll see Carmine brother Anthony in the game.
# There's a 130 dollar bundle of Gears 2 that will include an actual Lancer. No, it's not a functioning gun. Note: The information about the bundle -- including pricing and what it will include -- is unconfirmed by Microsoft and is subject to change.
# Gears 2 is "just as much Dom's story as Marcus'."
# Dizzy's hat can be shot off in multiplayer. Dizzy is voiced by Peter Jason from Deadwood.
# The collector's edition of Gears 2 will include the photo of Dom and his wife that Dom actually carries through the campaign. He pulls it out to ask people if they've seen Maria.
# Both the comic and the novel are prequels to Gears 2 but take place after the first game. The comic stars a new COG soldier who makes a cameo in the campaign mode of the second game.
# Jack, the helpful little robot from Gears 1 has much more screen time in Gears 2.
# The panel showed off a Gears of War Xbox 360 adorned with fancy artwork and a red paint job. One side of the console showed frenzied Locust and the other showed COG soldiers.
# The Gears novel comes out on October 28. Karen Travis also wrote the Republic Commando novels and love writing about war. She quizzed the folks at Epic asking, "How do the soldiers clean the chainsaw bayonet? What does their armor feel like?" Cliff had no answer when she originally posed the question. At one point Ortega suggested that they use "Lancer floss."
# The Corpser is in the game.
# Dom's older brother Carlos, who is a friend of Marcus', is in the novel.
# Len Wiseman is directing the Gears movie, Chris Morgan is doing the script and Legendary Pictures is co-financing. Cliff is an executive producer on the project.
# The actor playing the lead role might not be the massive buff guy that people expect.
# Cliff enjoyed lighting things on fire and dressing as a ninja as a kid.
# Thirty percent of Gears 2 takes place in The Hollow (the Locust lair). Cliff made the distinction to ensure that people didn't think it was a "cave game."
# People think Jon DiMaggio is hilarious. Especially when he converses with himself in the Bender and Marcus Fenix voices.