For the most part, this is a well written, well organised mini adventure/quest. It proivides some nice color to an otherwise dry section of DotMM. I does however have some flaws and that's why it only gets 4 stars.
There are only 3 main encounters the PCs must face to complete the story. The first one takes place in a spider den. I found that the sheer number of foes made that encounter drag on for WAY to long. 3d8+4 giant spiders AND 3 ettercaps? Experience should have told me to rethin that instead of running as is, but I just rolled the die for fun and that was a big mistake. I would reccomend another DM to limit the number of foes to 1 or 2 more than the nuber of PCs. The spiders are supposed to "retreat to guard their eggs" if reduced to 1/4 hp. That does not make sense (at least to me) since the layout of the spider lair is such that the PCs enter it directly into the brood room. Retreating to the same room is not a retreat. I have the same complaint about the next major fight, which includes 14 enemy combatants as written, and the final encounter which includes 15. So my main gripe is just a recurring theme; too large encounters.
Secondly, and this is a matter of taste, I think the adventure shouldn't assume that the PCs are level 8. I think it should have been written for level 7 as indicated in DotMM.
Thirdly there are a few holes in the plot that could use some additional explanation. I'm not going to get into them specifically because I don't want to give too much away, and its not too hard to figure out how to fit things together, but it was a little annoying.
In the author's own words "while this supplement is by no means perfect, it should go a long way in fleshing out the Port of Shadows" I find that to b a true statement and ultimately, I reccomend this supplement.