Thanks SkyMilesInsider. Two questions that haven't really been addressed:

-do you still need Z inventory to use the day of departure SWU's?

-why does DL feel that DM's won't "abuse" the "unlimited free changes" on award tickets that they claimed PM's did? Granted, there will be fewer DM's than PM's but the same people who were PM's will gain DM status, thus the same problems.

I tend to disagree with you that more PM's will use the SWU's now that they include day of departure. Most PM's would not even buy an M fare unless they were guaranteed the upgrade (i.e. there was space available for the upgrade at the time of ticketing).