So I've put about 50 hours into Beyond Earth's expansion, Rising Tide, and thought I would share my experience thus far.
The big additions are: Four new factions as well as re-working the eight factions from BE vanilla. Water cities with more water units (melee and stealth). New buildings and Wonders for aquatic cities. Hybrid Affinities with new versions of many (but not all) generic units and some unique units. A new Relic system tied to exploring colony ruins, progenitor ruins, downed satellites, alien remains and razing alien nests. You can combine Earth, Alien and Progenitor Relics to create unique buildings and Wonders. A new Diplomatic trait/deal system with its own currency which completely replaces the old diplomacy system Beyond Earth had carried over from Civ V. More orbital units to play with earlier in the game making the orbital layer something you actively use and pay more attention to rather than just spamming solar collectors.
Overall Rising Tide makes the early game a bit more fun (the A.I. is still super passive on lower difficulties though), water cities and being able to develop water tiles really opens up the maps, especially archipelago and atlantean maps. The new factions are fun to use. Chongsu get lots of science bonuses from espionage. Intergr have a lot of Diplomatic bonuses. Al-Falah can convert city production output to science, energy, food or culture at vastly increased yields, which is pretty much broken right now. While the North Sea Alliance can move their water cities around very quickly (usually requires a number of turns). The Relic system and scaling bonuses from expedition sites make them worthwhile game-long.
The diplomatic system is both great and horrendously limited. It's great in that you can adopt different diplomatic traits and change up your playstyle mid-game. Make it so your military can farm science off of enemies you kill and then later make them stronger defensively. Increase the amount of health your cities produce early game then later switch over to science, culture or production. The A.I. will also have these same traits, one unique to their faction and three they adopt. These will define how they interact with you. It's great because these things are much more clearly visible in the diplomatic screen versus how they used to be. The A.I. will also constantly chatter to you while the turns process and you can see your status rising and falling with them and it clearly states why. These diplomatic traits are awful because on the higher difficulty levels these things become game-y and stupid reasons for the A.I. declaring war on you for. You don't make enough food...WAR! You don't have enough people...WAR! You don't wage enough war...WAR! It's just a value that rises and falls and it's not always a sane or rational reason for one faction to declare war on another. It becomes very game-y on the higher difficulty levels. By the first 100 turns most factions will sanction you on Soyuz, it will likely be all of them on Apollo. The warmonger penalty is also gone from the game now, the A.I. get some really aggressive personality traits in Soyuz and Apollo that aren't always rational. In fact some will start to like you as you destroy their empires and plunder their trade routes. It's really weird. If there still is a penalty for warmongering, I have yet to encounter it. You can absorb an entire factions empire and no one else will blink. It's really weird.
There's now a war score system in place but the A.I. largely ignores it.
You also can't modify deals anymore. For example you can't decline to take their shitty cities anymore. Before you could remove or add things, now you just take and raze. This game needs a basic casus belli system, which, oddly enough, it used to have in the old diplomatic system with the positive and negative relationship modifiers the other factions used to have with the player.
The game is still balanced to 300 turns whereas Civ V is balanced to 500 turns. Beyond Earth games are short, there's an early game, a mid game and then it's pretty much done because you or someone else has trotted out their victory wonder and will win in x number of turns. Late-game units rarely have any time to shine. There around for 20 turns and the match is over.
Hybrid Affinities do not have their own victory conditions. Nor do you get Hybrid variations of all the base units. Rising Tide does not add any new wrinkles to the end-game, such as it is. Without their own victory conditions, Hybrid Affinities are kind of aimless. Purity is great if you want to build wide and have a large empire, Supremacy is great if you want to warmonger with a massive army, Harmony is great if you want to build tall and have a small focused empire. The Hybrid Affinities are just sort of there if you want...because. You still have to have a victory wonder lined up by turn 300 (Soyuz and down) or 200 (Apollo). So you have to have 15 levels in one Affinity to get its victory wonder out in time. Hybrid Affinities are potentially a waste of time.
There are a number of bonuses, ship loadout options, for Beyond Earth that are tied to owning and playing Sid Meier's Starships. One ship loadout option provides you the ability to build Colonists and Explorers in half the usual amount of time, another reveals expedition sites on the world map as soon as you land. You can abuse these two loadout options by going Prosperity to get Explorers the 3 extra expedition modules (you can rush this with 3 Virtues), go two levels of Supremacy to get another extra module and then the Laboratory building quest to get yet another. You can have three or four Explorers with 6 Expedition Modules scouring the world early game just raking in all of the resource pods and expedition sites. You really only have to compete with the A.I. over resource pods. They gather a single expedition site but then never refresh their explorer's loadouts and eventually they have no explorers. It's so open for abuse. They've promised a patch or two for Rising Tide. It's less of a mess than BEV was at launch but there's a few things that will need patching/improving.
TLDR: Overall though Rising Tide is a lot like Gods & Kings, it makes Beyond Earth more fun to play, makes the early game more interesting but there are still things that need improving in the mid and late game. Like actually having a late game.