Just went to WDW a few weeks ago. It did seem this time that Space Mountain was jerkier than usual. I did not enjoy the ride as much as I had in the past and felt like I just had to "get through it". We also took trips this past November and last January and it seemed to me that it was not as jerky then. I suspect that I rode in the front car more often in our earlier trips since there were only 2 of us and my son always lets me go in front of him so this may be the difference. Pretty sure I was mostly in the back car this past trip. Not sure I want to ride it again.