One thing that has been bugging me is that when you click an improvement to build from the planet screen, the cost is listed first and the effect second. I would say it's more intuitive to list first what the improvement does and list the cost later. After all when you are deciding what to build, you want to know what each structure does before factoring in the cost.

I have also been debating whether it would be better to have all the improvements shown in a grid instead of a list. This would allow almost all of them to be visible at the same time and potentially their icons could be made bigger to increase visibility. Then when you click an improvement it could expand into a rectangle and show its description.