No experience with the Keeley mods, but I did do one of the Monte Allums mods on a used DS-1 that I bought, and I thought it improved the pedal's intrinsically harsh & trebly tone quite a bit. Here's the link to the post:
http://www.thefret.net/showthread.ph...ghlight=allums
The Allums mod kit was good quality, reasonably priced, and came with good instructions for the the installation.