We went to the museum in February and were plesantly surprised. Our guidebooks and Trip Advisor were not high on this place but we found it informative and very interesting.
Yes, it is $12/adult to get in but every attraction in the Keys is expensive to get in. If you are visiting the Hemingway House as well you can buy a combo ticket and save $4 in total.
When we were there, there were exhibits on two floors and it took us a little over a hour to see it all. The first floor was dedicated to showing some of the treasures that were found from a Spanish galleon that sunk off the coast of the Keys. The second floor had treasures from other shipwrecks and an interesting exhibit on artifacts from a slave ship.
We didn't find the exhibits boring at all. The signs on the exhibit did a good job explaining about the life of the sailors on these ships and how the Spanish empire at that time worked. Besides the educational part, they had many cases displaying beautiful jewelry, silver, and other artificats that had been recovered from the shipwreck .
There is also an expensive store attached to the museum where they sell some of the treasure they have recovered. It is interesting just to browse.
I would highly recommend this museum, especially if you are interested in naval history.