Overall, it's still a good thing. As a Worldperks member I needed to do some travel in the Northeast (including a BOS-LGA shuttle). Having the option to accrue NW miles on DL makes them obvious choice when NW and CO don't fly somewhere, or don't do it at a realistic price point. Even with the 50% EQM limitation on DL's cheaper fares, that's still more miles than I might get on United or USAir.