GamingTrends tossed together a very nice review of Galactic Civilizations II: Dark Avatar and took the game apart examining the game based on a handful of categories; graphics, sound/music, controls, gameplay, and value /replay value.  Each section is individually scored with the final score of the game being the sum of the separate scores.

Dark Avatar received its highest marks for gameplay and replay value, with a good bit of attention paid to how no two games you play turn out quite the same, and how the player has a great deal of choice in picking exactly what sort of galactic ruler they want to be.  Here's a bit from the review conclusion, summing up what they thought of the expansion:

GalCiv2 is a great game. It’s detailed, well thought out, and planned. It has real science in it. It has real politics in it. It has drama and it has humor. It is a lot of fun and very thought provoking at the same time. You have an opportunity to play a role as the leader of your people. You can be benevolent or tyrannical, giving or greedy, and still win. It might not come out pretty, or even what some others may consider ethical, but it is possible.

To read the rest of this review, click on the link below.