I think Hallyday is a better pitcher than Lee, but I can't understand why Philadelphia really needed to make this move. I think Seattle makes out the best through this deal. I also think that both the Yankees and Red Sox are loving this deal more than anyone.
Lackey has already gone from the Angels to the Red Sox, so this could put the Mariners over the top in the division, or at least contend for it, if they can score runs. It also makes the division that much more interesting.