Initially I found it too bright for my taste. Not so anymore. I've posted this elsewhere, but I can't remeber where....Replacing the 5k resistor and 0,01 mikro F cap with the ones mentioned above made a great difference. It makes for a much warmer sound with more bass. My guitar is very versatile with this little mod. I use it 90% of the time. The other 10% is divided between my L-500XL equipped carved top "telepaul" and my little tele, mostly for sentimental reasons.
I do not modify the filter in any way. I just follow Bills advice.