Legacy status helps a lot in the admissions process, assuming the parents have been supportive of the school. Holy Cross has a lot of legacy kids and the school has started to play it up. For instance, they have a Legacy Lunch at Winter Homecoming for all the legacy students and their parents.
I have heard that legacy status is less of a positive if the student doesn't apply early decision. The theory might be that the student should know Holy Cross through his/her parents and should have it as a first choice. I do know of legacy kids applying early, being deferred to the regular pool, and then being accepted regular. The fact that it was their first choice probably helped. Frankly, that seems more reasonable than pushing legacy status after the student tries and fails at another school.