The 'short shifter' kits usually consist of two parts - the gear lever and the small pin that is for the box end. The reason peoples boxes seem to f*ck up is when this pin is fitted, as it does make the throw a lot shorter than just using the stick/lever. Ideally just fit the lever and be done with it - the feel is much better IMO.
My standard lever had TONS of play in it in the housing itself, not to mention the knob always fell off and was loose. When I took it apart it was down to the ball joint that goes inside the gear stick housing - it was made of plastic (cheers Renault) and was excessively worn (140k+ miles), not to mention the bushes on the bottom where the lever joins the linkage being sh*gged.
Whereas the 'short shifter' uses a steel rose joint inside the housing giving a lot more solid feel with no play whatsoever. The bottom bush where it joins the linkage is polyurethane too, far more solid.
I did like my gear changes with the standard lever despite the play to be honest - although thats with five engine mounts including the dogbone being a completely solid mount, so there is no movement in the engine what so ever really.
When I fitted the 'short shifter' lever it completely transformed it for the better, giving tight, crisp and extremely solid gear changes. Yes the gears are a bit closer, and it wont make you shift any faster - its all about the feel they give IMO.
You have to drive like an absolute f*cking moron who cant change gears properly to do any damage to the box (or fit the daft pin on the box end).