Huge Civ fan thinking of picking this up on pay day.
Is it any good?
If you already like Beyond Earth then you will enjoy Rising Tide, yes.
The new diplomacy system is pretty easy to understand and opens up a lot of different gameplay possibilities. I do criticize it for being a bit shallow and making war (surrendering) somewhat unfeasible at the moment, but it's something fresh at least.
The new units are all pretty fun and vary drastically from one another as well. Aquatic cities are easy to use and keep things fresh as well. I have no complaints here, really.
The early/mid game has been entirely revamped due to the presence of artifacts, giving new importance to exploration, so that's something too. There are also new quests that are triggered by certain unique structures that involve scavenger hunting to complete for a certain bonus. Those are nice too, I guess.
The new sponsors are a bit boring, though, and some of them are very unbalanced. The German one standing out as being quite ridiculous late game.
Do you even understand how the game works?