I've not got this pack yet because I'll soon leave town for nearly a month and can't play anyway. But another thing that bothers me is the milestones. I have 600+ sims, and if the game keeps track on everyone's milestones, I am afraid it will cause lag, without me really gaining anything. If it makes my game unplayable (low end computer), it will not be worth it although I like the new world and the dynamics.
But - now that I read that "old" events will be listed as milestones it sounds like most of these details are already being handled "secretly" by the game. So maybe I should not worry so much for extra lag, after all...