Well, my estimates for long-term consequences would probably be:
Soylent is fine to consume occasionally -- 98%
Soylent is fine to be a major (but not sole) part of your diet -- 90%
Soylent is fine to be the sole food you consume -- 10%
What exactly do you mean with fine?
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.