My reactions are these: Santorum lost his Iowa momentum. Romney kicked butt, as expected. Paul did not exceed expectations, but seems to attract young voters - not sure why since he's a cranky old guy. Huntsman got a boost but would have been more impressive if he' beaten Paul.
Perry put in no effort and his results reflect that; he's spent the week in South Carolina where he believes he has a much better chance. If Perry does poorly in SC expect him to quit. Ditto Gingrich, both he and Perry expect South Carolina to be where they "catch fire." My guess...they're deluding themselves.
What interests me is that each of these candidates speaks to a distinct segment of the GOP. I stand by my prediction that Romney will be the nominee, unless he says something monumentally stupid.