On to the new features.
Starbases are essentially capital ship emplacements. They have properties similar to capital ships, in that they have upgrades that are possible. Only instead of adding them when they gain experience, you just pay for them. And wow are they powerful. For example, the Advent starbase begins with two drone squadrons. Three upgrades later, the can have fourteen. Another upgrade increase hitpoints, shields, and regeneration rates. I fought a starbase with nearly 14,000 hull strength alone. It's just nuts. Starbases are just an incredible way to lock down a given gravity well, including suns!
Another new addition is mines. Although a small addition, this is another good one. Although you have to do a little bit of manual action, you can fill a whole gravity well up with mines, blunting a possible attack or completely eliminating small ships moving through your territory.
I'm still getting into more of the changes, but I have a pretty positive view on the entire expansion. Really adds some new content where there were options lacking before. For $10, it adds a good deal more to an already deep game.