The shortshifter kit is 2nd on my list (cup kit is next), but I want to get a clutch stop at the same time too.  About how much labor is that to get the stop put in and the clutch adjusted (Just an hour I'm thinking?)?
blast - a short shift kit will do a few things.  It will lower the height of your shift knob, shorten the distance travelled to 'get' into gear, and in general gives it a more fluid feel.   The shortened distance means you can essentially shift gears faster (once you are used to it).  This coupled with a clutch stop (shorten your clutch) speeds up your shift too.  (or can..)
Lots of the cars at the meet Sunday had short shift kits, I was absolutely in awe - it feels so much better to be lower like that..   I'm totally sold.