I've been playing a number of skirmish games against the AI. The random maps are interesting, but I'm hitting a recurring problem with the AI players and Diplomacy. (Aside from the usual selection of impossible missions, like attacking someone on the far side of the galaxy, or destroying 10 tactical structures at a point when all the players together probably don't *have* that many.) The problem is, that the AI players all seem to end up in a cease fire/alliance with each other. It takes a bit longer if there are more players, but if I'm playing against two AIs, they'll always end up at a point where they don't shoot each other. Since there is no spying or sabotage option, there's nothing I can do to break up this alliance. Against two AIs, this is annoying. Against eight AIs, it means that I automatically lose. (I am *not* a tournament-quality player, and I don't have the "mad skillz" to hold off what amounts to a fleet that outnumbers me at least four to one.) I realize that I can lock the teams, but I like there to be a little uncertainty. Also, on the random maps, if I lock the teams, my allies have a suspicious tendancy to end up on the far side of the galaxy, surrounded by the enemy, and are promptly wiped out.
As far as the Diplomacy in general, it would be nice if it wasn't quit so one-way. One of the things that's pretty standard in turn-based 4x games, and even some RTS games, it the ability to directly give resources, ships, and even planets to an ally, and/or the option to bargain with them for those items. ("So, Mr. Bond, now you need my help. I'll give you a small fleet of assault cruisers in exchange for 10 bazillion credits and that asteroid mining base on the edge of my territory.") It would also be helpful if there was some way to offer missions directly to an AI or another human player.