Sins of a Solar Empire released its second and final micro-expansion yesterday, Diplomacy. Unlike the previous Entrenchment, which put in new units like starbases and artillery cruisers and mines, Diplomacy adds more subtle changes to the game in the form of differences in player relationships. Probably the most exciting feature is the ability to issue missions to pirates and other player factions in the hopes to deliver a feint or put pressure on another opponent. Also added is a diplomatic victory option for those particularly suited to owning a quadrant without all the annoying rebuilding after planetary bombardment. More information is available in a guided tour from an Ironclad developer.
Although I've been in the beta program, I'm eager to try the 1.0 version. We'll have to get some multi-player set up!