Pirate Borg is Mörk Borg with pirates, a more sandbox feel and a ship combat system that feels like it belongs in Pathfinder.
The book, much like Mörk Borg and Cy:borg, has a distinct art style, light and fast rules (besides the ship combat), lots of tables for stuff and skimming the surface idea when it comes to lore/background. Add to that a neat summary of rules in the back, decent index, intuitive character sheet for new players and it's overall just a really nice rpg book to have.
It also continues the Borg paradox of being a weird book, but thanks to the index and rules overview in the back it's incredible to use in play. Statblocks, motivations, everything has easy access info for use in play, easy to find stuff and just a joy to deal with. It has to be said that some of the page spreads are hard to read for regular eyesight at times, so it can be a struggle for people that struggle with iffy color/font combos.
Had a lot of fun with chargen, the light and fast rules plus the sandbox approach to being a pirates in the cursed caribbeans when I played. The ship combat was not fast, intuitive nor fun. Too fiddly, too many detailed rules and too "boardgamey" for my tastes.
Overall a very nice book just to mine from and do the odd one shot ON LAND with. If I find (or come up with) more rules light sailing/ship combat rules I'd prolly love the game even more.