We've done the eco tour twice now. As others have said it's worth doing and the refreshments are good. The crew is very pleasant and works to make it as enjoyable as possible. Binoculars are provided and there are bird books to look at.
Unfortunately on our last trip there wasn't much wildlife around and because of this I found the return part a bit boring. But obviously it's a matter of luck as it's not like going to the zoo where the attractions are captive!