did that last week. Works fine, but you might have to make sure your keys aren't too close together. IE for second player if you using the arrows (up, down, left, right) and the keys 1,4,5,6,3 on your num pad for your buttons, they might lag because they're too close together. This is our settings for the two keyboards setup
player 1)
direction: w, s, a, d
buttons: j, u, i, o, l,
player 2)
direction: f, c, v, b
buttons: 1, 4, 5, 6, 3
Then it doesn't have much input lagg (at least we didn't notice it anymore)
hope that helps