negative:
there aren't any. But then again, maybe i'm not the right person to answer this quesiton
positive:
1. you can use more then 2 player shirts and 2 gk shirts per team, without having to edit your AFS file before each game.
2. texture boost for kits. (Konami's LOD algorithm is a bit poor in pes4/we8, which is clearly visible on PC, but with kitserver's texture boost you can fix one of its problems - improve kits appearance).
3. extra balls (although this is not very important, as the game itself has the ball selector)
Here are some screenshots to see the effect of texture boost. To make the comparison clear, i inserted a Holland home shirt into Russia's home kit slot in AFS using Graphics Studio 5.01.01. I set kitserver's texture boost option to 1 - meaning that only textures from KDB are boosted. Then started an exhibition match between Holland and Russia, so that they both wear the exact same shirt, but for one team (Holland) its texture is boosted, while for the other (Russia) it is not.
1st image: camera is really close to the players. No difference in shirt appearance.
2nd image: camera is a bit farther away. You can see now how the #5 shirt starts to deteriorate (white lines start to break up, circle in the middle is not smooth anymore), while #10 shirt still looks good.
3rd image: camera is farther away. Same effect as in 2nd image: #10 shirt looks better than #5.
