So, here are some thoughts after my third game.
Settings: AI - Hard; Alien aggression - High; playing Noxium Corp (Beta 1.1.0)
Overall summary: Having fun, but AI needs to come after you if you are nearing victory and vulnerable.
Longer version: I won an economic victory playing Noxium on turn 316. It was fun, but the AI wasn't aggressive enough. I think the secret seems to be maintaining military parity in the early game, and then building strong diplomatic relations which then allows you to slip behind in relative military strength without significant consequences. In the three games I played, it was only in the second game when I neglected the military early that the AI went all out after me.
By the end of the game my military had slipped to between 1/4 and 1/5 of everyone else's (from the useful stats on the victory screen), and had been behind for about 2/3s of the game. I only had a non-aggression pact broken once, and that was early on, and I quickly fixed that by going on a massive military build up and schmoozing the AI.
If I'd been forced to maintain military parity there was no way I could have devoted the amount of resources I did to building credits and thereby victory would have been stalled.
The game actually flags when you are within 75% of victory, and jokes about ganging up on the leader, but nothing eventuated.
The problem for me is how diplomatic relationships are modeled. This is a problem in most games as they don't seem to model real-world geopolitical relationships but seem more based on a personal relationship model (e.g. liking, feeling generous, angry). This is not the place for a dissertation on geopolitics, but countries typically work together when they have shared geopolitical goals, and fight when those goals conflict. The game doesn't model this (and most don't), but the two things players compete for in the game are territory (if you have adjacent empire's expanding into the same area), and victory. It is these areas of competition which should drive relationships.
In the long term all the players are enemies (because only one can win - I haven't explored the alliance system yet, so that may modify it), but the stand out leader close to victory is clearly everybody's enemy (Of course dog-piling then becomes a problem, but not an intractable one I believe). But in the short- to medium-term some players are more threatening than others, and the relationships should be built around that, not around mechanisms like praise. A short-term alliance to cut a mutual enemy down to size, or intervening to support a weaker player against a stronger one that borders you that you do not want to gain power, should be the kinds of calculations the AI is making. Just my 2c.
As a side note, I'm really enjoying the rolling beta concept.
Rolling cold wargaming dice since 1974.