Let me add another comment about combat, as well:

I've attacked some planets (mostly mining colonies) and the end result is almost always that I take the planet and I don't lose any ships in the process. This seems unbalanced.

One would assume that any combat is going to result in a loss of ships, whether ships vs. ships, or ships vs. planet. Also, if I do attack a 400m population planet and lose, I should probably take some of the planet's population down with me in the process.

Spartanius was planet hopping taking my mining colonies and I don't think he lost any ships in the process. When I sent my fleet to take them back, I hopped from planet to planet and as far as I can tell, I didn't lose a single ship in the process.