Played this on Medium in one go, didn't have to play any mission twice, this should be played on at least Hard difficulty if you want anything resembling a challenge.
One thing that caught my attention was that in the subspace chase mission, the Shivans didn't launch any fighters to escort their bombers. Without any cover or shields, the bombers die too easily. I'm positive that the Julius didn't get hit even once in that mission.
Not amazing, but quite enjoyable and solid. Hard to find many faults in it, other than it being a bit short. Good job, I'm looking forward to chapter 2.