I've owned mine for 6 years, and no matter what other OD pedal I buy, the Klon is still the king. Bill Finnegan only makes one pedal, and he somehow hit the nail on the head, which is why he covers the circuit in black glue to keep everyone from reverse engineering it.
The sound is like a richer and more robust version of your amp, which has a nice bouncy tube feel under your fingers. At 9:00, it's a nice rich clean boost. At 11:00, it starts to sound like a tube amp breaking into smooth OD.
At 1:00 it's a nice smooth OD, which is sort of like a Dumble or Two Rock.
It's not a crunchy or harsh sounding pedal. It just melts into the sound of your amp and feels like you just took your amp's volume and gain knobs and set them on the floor in front of you.
The TS-808 has a mixture of clean and distortion and a high-mid hump.
The Klon has a gradual increase in gain that sounds like natural amp gain, and if it adds mids, they're balanced with nice lows and creamy highs.....there's not an exaggerated frequency.