I can't say that my review is unbiased since we bought a 100L and 500L iStill NextGen and will be hosting a training seminar with Odin at our distillery:
https://twotalldistilling.com/classes/
But I can tell you why we decided to go with iStill. I have an engineering background so I approached distillation as a series of steps with a goal of consistently making a great spirit. I visited distilleries and asked a lot of questions about process control and tried to learn more about the science of distillation. Traditional stills are beautiful, but they can be hard to control and a lot of the distiller's time was spent watching the equipment. In the back of my head I thought that there had to be a better way.
Fortunately, a friend of mine built an automated home brewing system:
http://www.ni.com/newsletter/51643/en/
and I figured I could do the same thing with a still. But while I was searching for a base still to build off, I came across the iStill site. I contacted Odin and he was already building stills with the type of control I wanted. It was an easy decision to buy iStill after I understood all the thought that had gone into it.
When I talked to Odin I realized that he doesn't just make great stills, he also wanted to understand the science of distillation. What this meant to me as a new distiller was that I didn't have to go through a bunch of trial and error testing to come up with a great spirit. And we could easily repeat recipes that we liked.
We have a small distillery and wanted to automate as much as possible. This means that we get to spend our time developing new recipes and doing the things that we enjoy. This wouldn't have been possible without iStill.