Good feedback here. I've got a group sailing on Liberty of the Seas in March 2008 and I went through a Travel Agent to arrange it. The booking is for 9 cabins, with a total party of 20 folks. I asked my agent to fight for a free cocktail hour for my group and the line agreed to one hour cocktail hour with food. I've sailed in groups of 15-25 once a year for the past 5 years and this is the first time we've been treated to anything special. I'm not sure if our cabins we book have anything to do with it, but this is the first time that we got one OS and two GS as part of our 9 cabins.
Hope to see what other stuff the may provide this time around. As far as the pricing, honesty, I've never experienced any "discount" other than the one free person after 8 cabins. Which by the way, you get a check for that amount 3-4 weeks after you complete your sailing. The amount is one full fare of a person in the cabin class that most of your cabins are booked in.