I pretty much knew that if I won, I would not use it because the prize to me is winning, not getting to go on the rides.
I won it at Epcot, and I had already gone on Soarin, Test Track, and Mission Space before I won. Honey I shrunk the Audience and Living with the Land didn't need fast passes, and I didn't think Malestrom was worth using only one tab, so I got a regular fast pass for that.
If I win another dream fast pass at Epcot, I will definitely use it or give it away. If I win dream fast passes at the other three parks, I will save them in original condition unless I win twice in a park.