RJ,
I have the BD short shift on my 6-speed. The throws "feel" very much shorter, although BD only states there is about 20% difference. For me, it's much more comfortable to drive. Before, I always felt like I had to "take a trip" with the shift lever, since the travel was more than I could easily make with just my arm movement. Now, it's well within the arm action, and I don't feel the need to put my shoulder into it as well.
However, be aware that the shortened shift action requires a bit more force, since the leverage is decreased. You need to put more "oomph" into the throw. Some people don't like this, since the 5600 already needs a bit more than some other transmissions. After all, it IS a truck transmission.
Hope this helps,
John