There was one at the Houston Amp Fest and I thought it sounded pretty good. But, catch this, the owner of it offered to trade it to me for my Two Rock. (which I promptly declined) That owner sold it within a few weeks and I'm pretty sure ended up buying a Two Rock.
Getting back to your question... they are handmade in California by Fred in limited numbers. They are expensive, very touch sensitive and they sound fantastic. The one that I heard was a 6L6 version. (ERT37?) No master, no reverb (if I remember correctly)
I thought the Two Rock smoked it. For that kind of cash, you need to play a lot of boutique amps to find the right one. I went through several amps trying like hell to get the perfect tone for my ears. I have bought an sold a lot of amps in the last few years until the Two Rock. This is all about my ears and my guitars.
There are probably a huge number of folks that prefer the /13 to the TR though. Gotta play them or buy them from someone with a good return policy.