Had a B&M SSK installed about a month ago in my -99 C4 and I love it!
First I thought it was almost too short (minus 37%), but now it feels natural. Gave the 996 that "mechanical" click-click shifting action that was missing before. In comparison stock action felt like an old VW tranporter...
I would rate the SSK as #2 on my list of mods, right after the essential sport exhaust. (Fabspeeds in my case)
B&M are OEM for Porsche, quality and finish is impressive. Price is right too.