Bought it last month on that other storefront. This is a legit good game and I wish I could've bought it on Gog although I know sometimes updates on Gog can take a little longer so maybe not my favourite platform for Early Access, but it's an incredibly promising game already and I've put 151 hours in it thus far. If not brought onto Gog while it is in Early Access, then at least once it's properly out. I'd happily buy it again.
The game reminds me a bit of Sid Meier's Pirates!, but with a significant splash of Man O' War: Corsair(Other people have said AC: Black Flag and I think I can see that from what little I've seen of that game, but Corsair is the comparison I can make).
The character creation is good, the sailing and sea battles are fun, the building is really good although you don't have a lot of stuff to build initially, but part of the gameplay loop is gaining Guineas to buy new patterns and blueprints to make things. You can also find additional building stuff on islands or via quests.
I love the sea shanties and sailing songs although I hope they add more, I'd love to see songs like "Ben Backstay", "Spanish Ladies" and "Don't Forget Your Old Shipmate" added to the game, but it IS in Early Access so we'll have to wait and see.
The procedural generation of worlds is good too and makes for a lot of easy replayability.