I think the Tempest expansion is amazing. I'm playing as the new race, with 8 islands, but only ~30'% of the map is land. Huge is really huge in this game, so the Islands are still pretty large. I'm also playing with Huge Regions, but they still will have a few regions per island on average.
I started off on a long penninsula, so you might think the growth may be retarded, but the Morgwar love the water and get all sorts of bonuses from it. They also start off with Shipyard, so I immediately set sail and began exploring. The first thing you notice in the expansion, after the new race, is the weather at sea. You have Turbulence, which actually increases your speed. You have Fog, which you can see out of, but enemies can't see into. It also provides a defensive bonus in battle, as Forests do on land. You have Rain, which on Auriga is pretty violent, so it actually increases upkeep and lowers morale. Finally, you have lightning, which will lower health by 45% if you are foolish enough to end your turn in it, or just 15% if a storm brews up on you at the start of the turn. I'm not sure if you lose 60% if you end and begin your turn in a storm. Weather is only factored onto the sea, and if any of you have weathered a storm at sea, or even on a large river or lake know, that is is reasonable. There's no where to take cover, as there is on land.
They've added sunken ruins in the ocean for you to search and the new Minor Faction, the Fomorians, are only found at sea. They inhabit Bastions, Manufactoriums and Listening posts. All may have one or two resources associated with them. Control the Fomorian outpost and you control the resources. Like the other Minor Factions you can either conquer them, or run quests for them. They've added a ton of new quests. They are much like the land quests, but I enjoy Amplitude's writing and I continue to enjoy these quests and all the flavor it adds to the game world. One quibble I have, is that the Morgwar were enslaved by the Fomorians, but seem more than willing to run some errands for them.
Another quibble, is that they only heroes I've seen for Morgwar so far, have been Amphibious, but they still rely on a transport at sea. While you can boost your abilities as you gain level, I would have liked to see a true amphibian, or even an aquatic only Hero. Maybe there is and I just haven't seen it yet. However, I'm not even sure if the different races have multiple heroes, or if you need to hire different species to get different hero types?
Amphibian simply means you are able to travel along rivers at 3 times the speed of land. I may try my next game with more land, but keep lots of rivers and lakes. It might make it fairer for the other species. With this water world, and only playing on Normal because it had been a while since I last played, I find myself outpacing everyone else.
In the First Era, you have your Amphbious support unit and a very fast, but somewhat weak Boarding Vessel that you can research. You are relatively safe however, as the wandering Fomorian units only seem to attack you after you initiate hostilities. So, you are free to run some quests for the Fomorians and gain some of their aquatic outposts peacefully. The Faction Quest will eventually lead you to start fighting them, but that isn't until the Second Era.
Unlike other Minor Factions, you don't assimilate the Fomorians, you merely take control of their holdings. Also, they need to be garrisoned, because any wandering unit can simply waltz in if they are unguarded. The only bonus your receive is a variety of different FIDSI depending on the holding and the associated resources. The resources themselves being the main reward. At first, many of the holdings will have an unknown resource, as you need to wait until someone in the game reaches the Era appropriate to reveal the resource.
The Morgwar were genetically designed to rule the sea, but they were also given psychic abilities. They can mind control wandering units. They spend a decent amount of influence to initiate the mind control, and then pay a generous dust upkeep to maintain control. The roleplaying is strong here, as it is pleasing for me to imagine the formerly enslaved mind controlling the ex-masters.
So, Amplitude has taken this wonderful world of Auriga, with it's multitude of Anomalies and varied terrain and now added weather to the oceans, so they too feel alive. They've added another flavorful Major facton and a new Minor Faction which brings the total to around 20 Factions. I really can't think of too many game worlds that are this diverse. I remember being very impressed when this game was released in Early Access, and since then they've added so much stuff that I'm truly impressed.
The only bad thing will be going from this game back to ES2. I think it will still be a great game, but I'll really miss my time on the Surface of Auriga, to only see it replaced with an orbital view of a blue marble in the vastness of space.