DAMMIT! I forgot Saltmarsh.
Also -- they didn't reprint the rules for ship in Spelljammer?
Nope!
The only thing they have listed for the Spelljammer ships are HP, Crew, Damage Threshold, Speed, Material(AC), the weapons listed on there, Speed, Keel/Beam, Cargo, and Cost.
The weapons are listed with their own Armor Class, Hit Points, Costs, and how Many actions it takes to use said weapons. That's it. No mention of helms/Sails(for ships that it makes sense for), or stuff like that.
COMPARED TO:
Sailing ships are fast-moving designs focused on travel. Warships are slower but more heavily armed vessels capable of taking on more car...
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Not a single mention of stuff like Captain, Quartermaster, First Mate, Bosun, and other positions. There is a sidebar style box on pg.25 of the Astral Adventurer's Guide that states Shipboard Weapons are better for far away targets and when in close range, your PC's weapons/spells are better. Now, considering the Spelljammer ship weapons require more than one action to load/use, that makes sense...........................................Unless you have Acquisitions Incorporated/Ghost of Saltmarsh, which states that Ships can make
THREE actions along as they have a high enough crew levels. Which means that using Shipboard Weapons won't "actually" be that annoying to use compared to how it was stated earlier.
Also: no Spelljammer ships have any ability scores. Not even STR/DEX/CON that ships usually have scores in. And of course, nothing is mentioned of stuff like Crew Quality scores, Downtime, Ship upgrades or even the possibility of a Mutiny.
Honestly, if it probably wasn't for the 64 page count, it's quite possible that the GoS ship rules would've been reprinted.
So yes, Ghosts of Saltmarsh will greatly enhance your 5E Spelljamming in a number of aspects.