I've never had a dealer show any enthusiasm about trading. The best that I've seen is a local Bad Boy/Grasshopper/Gravely dealer that actively helps you sell your used equipment online. He does it in good faith and tries to get all he can for you.
This approach seems to minimize the competition that used equipment might offer toward his new inventory, and at the same time makes his customers feel better about buying his new stock.
Before this guy, it seemed that every dealer I ever tried to deal with, would simply make a really lowball offer in an effort to appear cooperative, but he really didn't want to fool with the used equipment.