I've been playing it for several hours every single day since its release and I've loved every minute of it. In my opinion Elemental is already one of the greatest games of all time.
Last night, I started a new game as Tarth and spawned next to the Capitar on "normal" difficulty. By about turn 100 the Capitar had about 15 cities and had completely surrounded me. Then they declared war on me and the fun began.
Wave after wave of their army came pouring over the mountains upon my settlements. I only had a few small squads in each city and I was vastly outnumbered by the enemy. Amazingly we were able to fend off the first wave that targeted my capital city, but just barely. At that point in time I had my sovereign far away from my capital with a small squad of spearmen. While I was trying to race home, I stumbled upon a smaller Capitar settlement that was lightly defended. I was able to take their settlement, but with some heavy losses.
Right now I'm fighting for my faction's life against all odds. It feels like I'm replaying the American Revolution, where the enemy vastly outnumbers me and I must use every one of my soldiers intelligently to win. I have never, ever, ever had this much fun in a 4X TBS before. Even war in Civilization has never felt this good, they always felt really plain and boring and I never cared about my limitless number of units. In Elemental each of my citizens feel unique and when I lose one, it actually hurts.
I don't know where people get the idea that the AI sucks, they have been tough every time I have played. In reality, the city spam strategy is the only hole left in the game that probably needs to be fixed up for the AI to kick butt.
Also, stability has been fantastic. I have never had a single crash in ALL of my time playing. The thing I love about the game is how quickly I can shut the game down if needed. If my wife walks in the room and wants me to take out the trash or something, I can have the game saved and shut down in about 10 seconds flat. That's performance I haven't seen in a long time in games.