The acting of several lead actors is really bad. Avasarala (the "undersecretary"), Bobbie (the "marine"), Jim Holden - they all portray characters in a way that is utterly unconvincing. Every scene with Avasarala is a scene that can't end quick enough. She looks like a bad impostor. Bobbie is miscast so severely it's on par with the "bitchy teenager" Anakin from Ep2 and Ep3. Holden's facial expression for determination is that of a man about to cry. In fact, he looks like his dog just died in most of the scenes.
The story and the universe is excellent, the rest of the cast is really good, but it's not enough to balance it all out.