I like this idea because it means you can completely control what you are putting into your body, and adjust the levels when needed. It seems very likely that this Soylent drink is much more nutritious for you than what you're probably eating right now.
However, I think an issue with this diet is that if you've been on it for an extended period of time, your body might reject any food you give it, disallowing you to eat traditional food when you want to. Also this liquid diet will probably get very boring after a while.
What do you think?