The Vow was considered by many to be a surprise success, but there were many elements that made a big hit not hard to see coming (being the only legitimate date movie in a marketplace that was starved for one around Valentine's Day, having stars who have both enjoyed previous success in the genre). That whole weekend (February 10-12, 2012) was a crazy big frame altogether though.
By the way, I don't know if this was mentioned but, according to BOM, The Rover posted the worst opening for a wide release since the notorious Oogieloves from almost two years ago.
What were they thinking releasing such a downbeat movie with stars that aren't draws on their own in the heart of summer?
The Regal E-Walk and AMC Empire are located right across the street from each other (I saw Frozen at the former when I was in NYC for Thanksgiving last year) so they show different movies, FYI.