I'm not sure how I feel about having Prestige lobbies... this has the potential to seriously fracture the player base down the road.
Well this will mean that all non-prestigers who have all the guns and perk upgrades will get to play against each other, while the prestigers who are still working on the guns and perks get to play against each other, thus leveling out the playing field. I think there are enough people in total playing the game that you won't have to worry about not finding a game.