Soylent is a good "filler" food, definitely better than unhealthy snacks, but I wouldn't drink it all the time.
While staying in US for a few months, I ordered a weeks' worth of Soylent powder to test what it's like on my own skin. It didn't contain caffeine like some Soylent products but, as stated on the website, contained all the nutrition need for a human to function normally while drinking only it and eating no other food at the same time. And, compared to prices of food in New Jersey and New York, it's a really cheap alternative.
A single bag is supposed to be enough for a day. The only ingredient missing from the powder is water which has to be added to it to create a brownish, cookie dough-like concoction. Not just its look but also taste reminded me of cookie dought, which is to say it's rather neutral and can be improved by adding fruit, for example. Mixing the powder with water can be done with a supplied pitcher. It's included in the first order. It's a big thing and kinda unwieldy to shake when powder and water are inside but probably the best way to mix the two, because it can be later used to easily pour the final mixture into a cup or some smaller container throughout the day. The powder has a very long shelf life when unused but once mixed with water, it should be drank with about 24 hours. Due to this characteristic, it doesn't have to be used right away. When I used it, it took me way longer than a week to finish the whole order, because I often ate regular food alongside it. There were also days when I drank it almost exclusively and when I barely drank it at all.
Soylent does get boring after a while but I didn't experience any health issues while drinking it, except... the "flatulence issue". Soylent makes passing gas a noticeably worse experience. Restraining yourself from passing gas near other people is good manner either way but after drinking Soylent, I'm pretty sure it's a legal offence.
At its current state, I trust Soylent can be a great supplement to a busy lifestyle. It's super easy to prepare, can be drank quickly before work if there's not enough time to prepare anything else to eat, taken to work instead of a "regular sandwich" and eaten late at night when the fridge is empty and all stores are already closed. Soylent doesn't annihilate hunger but does a decent enough job as a "filler".
I will definitely try the caffeinated version of Soylent if I ever have a chance.