Depends on reason for going. Not much to do if family. There are other more family friendly places in Florida. Key West is about drinking. But you can see the Atlantic and see the Gulf.
Just there. We had a nice time staying at the NAS. (military ID required). Unless you are big into drinking, think about another place.
Yeah. If you stand in the right place, you can watch a piece of eelgrass move from the crappy looking water of the Atlantic into the crappy looking water of the Gulf. And back, if you've time the tides.