This past weekend I got together with Spork and we installed the short shifter on her car. It went quite smooth and wasn't a difficult procedure. You can see the full write up on how to do the install here:
DIY short shifter installation
http://mirageforum.com/forum/attachm...0&d=1458571046
As for feedback on it, I got a brief drive before hand and afterwards. It definitely was not nearly enough to get used to things. Spork has only had the car for a couple weeks now too. She can add her thoughts if she wishes. She went into this not expecting to keep the shifter, but decided to give it a try knowing we can swap the old one back in if she wants. Also, this is on a brand new Mirage with less than 1k miles on the odometer, so everything was still getting broken in.
Personally, I thought the stock throw distance wasn't too bad at all. Its definitely shorter than the Chevy Metro I daily drive. I like the bit of notchy-ness in the action. It gives you a positive feel to know what gear you're in and what you're going into. The Metro's shifter is more vague and I'm not a fan of that.
The short shifter enhances the notchy-ness a bit more. It takes a tiny bit more effort to shift, but not bad at all IMO. The new throw is quite short. I think a 40% reduction is a bit much, others may love it. I would probably back it down to ~30% reduction if I were to make one for myself. For example, when I shifted from 2nd to 3rd I knew I had gone to 3rd, but I couldn't totally feel the shifter move over as much as I'd like to. Thus, it lost some of the positive feel there. I have no doubt that I'd get totally used to it, just keep in mind I'm coming from the Metro. I didn't try to jam through the gears as it was a brand new car. The short throw really does give you the feel that you're shifting faster. It seems like a flick of the wrist gets you to your next gear which I do definitely like.