With all extras being added to GC2:Dark Avatar, my comment is to be very careful about feature creep and bloat. GalCiv2 is without a doubt a fantastic game. Don't break it by enhancing it, so to speak. Before the obvious rebuttals to that comment come, please understand: I want cool new features too! I just think care needs to be taken to refine what is there before taking on too many new things.

The UI of a strategy game is critical! As these games are complex by nature, without a clear easy-to-use interface they can become cumbersome.
It is important that the player understand the mechanics of the game elements as easily/quickly as possible (moderate learning curve). The effort expended should be on the execution of strategy (the fun part) not the comprehension/navigation of the toolset (the tedious part).

IMHO, the UI in GalCiv2 should be the #1 priority for improvement above any new feature. While not bad, there is a lot of room for improvement. In general, more information should be available with less clicks and the cause/effect of actions should be obvious. I know that UI improvements are slated for the expansion but I wanted to stress it again as I feel it's really important. If new functionality is added and UI usability not improved proportionately, it will be problematic.

I believe the two hardest parts of learning this game (and therefore the biggest barriers to entry for the not-so-hardcore) are:

1. MASTERING THE TECH TREE - There is a wealth of information here that you must understand if you are to research effectively. At present, it's like trying to understand at a huge map of the world through a tiny magnifying glass. To get information, you must click on a specific technology. Why can't research times/costs be shown graphically? Perhaps icons associated with a tech showing whether it allows a new building/trade good/super-project/etc. There are of course many ways to do it but the idea being more information with less hunting/clicking.

2. ESTABLISHING A SUSTAINABLE ECONOMY AT THE BEGINNING OF THE GAME - How many players go broke within the first couple of years? Perhaps more importantly, how many have no idea how to avoid this? The cause/effect of this failure is not clear. I had to read many forum postings before I clued in. It's not that I wanted to be told a winning strategy, I'm happier to figure that out for myself. But, as the cause/effect wasn't clear I didn't know how to make intelligent changes to my strategy. For example: Population growth (a value that is not shown anywhere I can find) is critical at the game start which is tied to your approval rating which is tied to tax rate. When you are running out of money it is counterintuitive that it can be helpful to lower your tax rate to increase your population and therefore future tax base.

Improvements to the UI could address both these issues (and others such as ship management, etc.) to make the game much more enjoyable without adding a single new feature! Learning to tweak your strategy is fun as long as you understand cause/effect. If you're just shooting blind by trial and error, it can get frustrating. As I said, I'm not suggesting that no new features get added! But, I think it's important that the existing UI be polished before moving on to bigger and better things.

All that said, I'm very excited about the expansion and have the confidence to preorder when it becomes available. Good luck with the bug-hunt guys! I look forward to trying the beta.