I just modded my buddy's daddyo yesterday, and I must say that it sounds 100% better. It doesn't have that "cheap fizzly distortion" sound.
The main thing is to replace the IC with a CMOS opamp. It makes it much more creamy and smooth. The rest of the mods follow along the lines of skewing clipping symmetry and lowering the high pass corner on the amplifier stage to add a little more "fatness".
I thought I would share the wealth with the DIY community:
http://www.geocities.com/transmogrifox/daddyo