Here's a really good review that I found for the CX-30. He got to drive the CX-30 with and without the Skyactiv-X engine which is very interesting. He does point out that the CX-30 feels more usable and agile with the Skyactiv-X engine.
There's also a short interview with Christian Schultze, the Director of Research and Technical Regulation Compliance at Mazda Motor Europe R&D, where he talks about how the Skyactiv-X is more efficient than previous engines by using compression ignition along with a spark plug.