They surely are fun, but sadly don't have any pics. The pro side is probably that in most cases you can build more freely without having to think of defending certain parts - if it is further out on sea. It really isn't all that expensive, you can just build on small existing islands you can find in your worlds. From there you can in most cases extend them to a certain amount (the height will prob be the limit as you may encounter some really huge waves more often). So for the building area you will only need stone depending on how large you want to build there.
Edit: And awesome stuff that was already posted!