A while since I played around with the Klon circuit, but I built a few different versions, and have compared one with both an early silver, and gold horsey. To be fair I think my clone sounded as close to either as they did to one another, and they weren't that different. Anyone that offered the "mix control" in the Drive block being essentially the same thing as the gain control in the Klon Centaur is right on the money. All the way to the left is a clean boost (really nice, warm, beautifully buffered clean boost), all the way to the right is a fixed gain TS style overdrive. If I had to pick a flavour from memory, I'd say Fulltone OCD drive with gain set pretty low. The "gain" control just sets the mix between these two. The thing I have seen no-one mention in the thread is the headroom, especially of the clean boost, in the Klon circuit. It uses a voltage doubler to run the positive and negative supplies at +/- 9V rather than the +/-4.5V more normally used in TS style drives. I always thought it shouldn't matter, but it really seems to. The clean boost is really clean and dynamic for transients, and has an "instant" feel you don't get from many other pedals. It also means that those dynamics really come through when you have the thing set into "reasonable" levels of dirt, especially with a lot of volume boost. It also means if you are battery powered you get the most bizarre weird sounds if the battery goes flat, and the DC-DC converter starts introducing background noise. They go through batteries pretty fast.
So, no, don't believe the hype by any means, but also don't get fooled into thinking Bill Finnegan didn't invent a truly remarkable and versatile pedal. Until people started making substitutes, there really was no substitute for high quality, low gain. They are also remarkable for driving other dirt pedals. I would love to see one in the Axe FX, but I bet you could get most of the way there with a FET Boost driving an OCD or similar block, and using the mix control of the OCD to behave like "gain", and the volume and tone controls on the OCD as with the Klon.
Liam