I like knowing exactly what's happening with the map pack ahead of time. I can make my own judgement call with a clear idea of what's ahead.
I felt I got stung by the Chapter 2 pack for GRAW1, which, after a few weeks/months of waiting I succumbed to peer pressure over and paid 1,200 points for. Literally 2 or 3 weeks later they were 600 points. I'm still bitter about that as I'd been waiting for an inevitable price drop. Just not long enough.
But with respect Gears of War, how will Epic/MS handle map packs for PC users when the game eventually (surely!?) arrives on the PC format? Same format I guess; pay to play early on 360, wait for cheap vs freely available on PC, or perhaps linked to Gold Membership for Games For Windows Live?