Of course, it could be a Romney landslide (mainstream Dems, independents, liberal and moderate GOP, business and fiscal conservatives). But, apart from social conservatives and evengelicals, there would be a "revolt" from popular Dems. So, let's say:
403 - 135
Palin would only be competitive with social conservatives, evangelicals and some blue white-collars (hence her good results in Appalachia, but also in Illinois, and short defeats in Ohio, Minnesota).
Palin would be trounced in North-East, in Rocky Mountains, in the West Coast and in Florida. She wouldn't be good with Latinos and business conservatives (hence, defeats in the South-West, including Texas, and in VA-NC).
Sure, a surprising map, but a very interesting one.
Maps from previous posts are far too optimistic for Palin. Romney is articulate, well organized, wealthy, etc. It would not be possible for Palin to win in big states like PA, OH, TX.
And, in IL, I think the "revolt" and sort of kamikaze votes from some Dems would be enough to have THE surprise of this "special" race.