I've bought DA soon after the release, bit I'm just starting to play seriously around now. Very addictive. However, I managed to forget most of what I knew about game mechanics, and so I had to re-read the manual and some forum posts.
It would be extremely helpful to have more tooltips that tell you what produces certain things in the game. GC already has that with approval, but many other planetary attributes are a mystery until you do tremendous amount of online research.
A good example would be population growth. I know that morality affects population growth, but I'm not sure how exactly. Wouldn't it be much simpler if I could just hover over population counter and see what is the growth factor and what affects it? Same thing can be said about pretty much any other number on planetary screen. What determines the amount of money a planet generates? I assume it's population, but I don't know the details.
To summarize: it would be very nice to have tooltips that explain how exactly do you get the numbers you see on the planetary screen.