I havent purchased yet either, but I keep checking here:
http://www.gm.com/automotive/vehicle...umer_IOU.html?
notice the current either/or - 0% for 36mo or 3000 cash back.
I'd like to get 0% for 60, but not sure when they'll go there for the 07s. My guess is within a few months. Even though the next V doesnt come out for a year, i'm betting they wont want 07s on the lot in 08. and $50k manual american made gas guzzlers arent selling like hotcakes. very niche market.
Note that if you use edmonds calculator, 0% for 60 mo is way better than 3 or 4k cash back at 6%