It has been mentioned about how SfSS is nice for GMs for a number of different reasons. To start, I DO like the adventure and am quite happy with it (will be starting this Saturday). However, it is strongest in the "2nd" half - basically after they get past the "fluff" encounters. The complaint that I have is in the claim that this is easy for the GM. My disagreement with that is that a "sandbox" (which this is partially) is inherently more work for one. On top of this. . .
the first "half" have three worthy encounters on board wrecked ships (one the PCs). These have enough going on on them that they need to be mapped out with your players. Now I am not familiar with pirate ships, nor (and especially) damaged ones that I assume have sections missing etc. It would have been nice to have had at least mapped for us.
This combination leads to a significant amount of necessary GM prep.