Actually they call it Mopac because of the Missouri Pacific railroad, but mo packed is also pretty good. I should know, I drive on it everyday during rush hour from 183 to Slaughter. :bomb:
Just picked one up about an hour ago in Austin, Texas. They had stacks of about 50 of them. This was B&M, so YMMV. It's listed here for $89.99:
http://www.bestbuy.com/site/olspage.jsp?skuId=8247266&st=guitar+hero+ii&lp=4&type=product&cp=1&id=1168045345487
This game is $19.99 at Target B&M. I almost purchased it last night, but my fiancee wanted Cooking Mama instead.
It is listed on the site for $57.99 though.