iceskatejen is correct. I or my husband have used them on two or three seperate occassions. It takes a little longer intially for them to verify how many days you have left on the ticket because, like iceskatejen said, there are cm's who don't know how to do it; but the cm's are aware that you can use WDW park hoppers at DL. At the time, they sent me to the gates and a supervisior had to verify the days while I waited. At the time, I was told the two park systems were not linked so they had to physically phone WDW to verify. That was about three years ago. It apprears by the comments on this board the procedure has changed and now you need to go to guest services.
I don't know what the scoop is on the new WDW passes with the "Magic your way". I thought I read somewhere that some of the newer WDW passes expire like the DL park hopper do. Is that correct?