Sometimes Iowa has NH as its boy toy, and sometimes not. It depends on the tone of the campaign, and what is emphasized, and what is not, and what the polls are showing as to who seems most likely to beat the Dem. But among the big three, winning Iowa probably would be a substantial plus, if it was reasonably decisive.
For the Pubbies, there's no Vilsack to make Iowa irrelevant. Iowa usually produces 3 viable candidates, I think it will produce only 2 in the GOP.
Usually there will be a big gap between NH and the rest. Not so this year, especially for the Dems. That plays to Hillary's advantage. She makes the Iowa caucuses irrelevant, downplays the cranky NH voters and then goes to the bigger states running nothing but TV ads. She needs to avoid retail campaigning at all costs.
For the Republicans, this works in favor of McCain, he has a lot of big donor money. He could be defeated by a (1976) Reagan, someone supported uniformly by the grassroots of the party, but if Romney cannot stake out that ground alone, he won't be able to overcome that natural advantage.