I'm not bothered about Space Mountain now until they install the new seats & harnesses to make it less rattly - hurts my head too much these days.
I am gutted that Thunder Mountain is closed on our dates though. It won't be the same without that. I am treating my DS1 and his Fiancee to celebrate their engagement - it is his favourite ride as well, and her first DLP trip.
It is too complicated to change our dates, or I would.
Rock n Rollercoaster is very similar to Space Mountain, but newer and smoother. Not quite as extreme as SM though, which has a higher height requirement.