I'm in favor of it, for the following reasons:
-It gives the rushees a chance to experience non-Greek college life and they will be less likely to "burn out" by senior year.
-The rushees have had time to get used to being their own bosses and managing their time as far as studying, etc. They also get to see whether they like that college in general.
-They have a chance to see how much of a part of the campus Greek life is and make a better decision as to whether it is right for them.
-There are fewer people who get "swept up" in it as part of the newness of college.
-They (hopefully) get to meet some of the members and make a decision from "real life" instead of just through 3 days of formal rush.
Now keep in mind that I'm saying this from the vantage point of a campus that did not have large houses to fill, and that had very lax "contact" rules - the only time the no-contact rules applied were during actual rush. For some of the schools I've heard about where freshmen are prohibited from going anywhere near the houses, I think deferred rush there would be a pain in the butt.