I've never ridden Mission: Space, as I have motion sickness issues and even the green side has no appeal for me.
As for ToT...we rode it for the first time last year. All of us were pretty scared of it going in (which is why we'd never ridden it before), but we all decided to try it once. My husband hates drops in general and totally hated it. He'll never go on it again. The kids (5 & 8) said they were scared of it, but I'm pretty sure I could talk them back onto it. It wasn't the drops that did them in...it was all the creepy Twilight Zone stuff leading up to it that they didn't like (as well as the creepy elevator loading area, which, IMO, is like a scene out of A Nightmare on Elm Street). I personally found the ride to be really fun and I laughed all the way through it. I'm a sad panda that no one will ride it with me, and I'm just not the single rider type. I'm hoping I can bribe one of the kids into riding with me in October, since we're not likely to return to Disney any time soon after that.