Chef Mickey's is a popular choice with a lot of people, as you can see from the responses so far.
We like to go to DTD our first evening, and we usually have dinner at Rainforest Cafe. We tried Planet Hollywood last trip instead, but we're going back to Rainforest Cafe next trip because we enjoyed it a lot more.
As CamColt said, the Boardwalk is another fun place to spend your first evening, and there are quite a few places to dine there.