It was very tasty, and I was quite pleased with the combination of flavors. It was also very time-consuming and fiddly. If I had a sous-vide cooker, I would totally make it again, but I'm not gonna do it by hand.
Note that the recipe makes like five times as much miso butter as you actually need. I am all about salty and umami, but really: you don't need that much of it. I think you could halve the ingredients and it would still work just fine. Note also that it's a lot easier to mix miso & the butter if they're both at room temperature. (I warmed my butter and forgot to warm the miso...)
I also made some cucumber-watermelon agua fresca. It was also tasty, but more importantly it reminded me of an amazing drink I had at a restaurant in San Francisco once, which I *think* was cucumber-honeydew-mint-lime. That's what I'm going to try next time I make agua fresca.