depending on what you use the bench for, they might stay tight for a while. but eventually, the holes will elongate (after all, it's pine), and then the table will start to rock.
if nothing else, i would add another cross piece lower to help the keep the legs parallel to each other.
my router table is actually fairly similar to that. i made some of these out of some scrap 3/4" ply i had laying around and bolted them onto the ends. they really helped the stiffness. i glued them together so they stay square.
and if you can cut a big old dado/housing in those 4x4s for another 2x4 across the long sides, that would help keep that direction from swaying or leaning
Last edited by Chris Curl; 05-21-2013 at 01:18 AM.