Your original post's attitude seemed to imply it was almost risky to consume this as it's made by people aged "20 or so". Not only do I find your age discrimination shocking, I also take issue with your sarcastic tone.
If you want evidence, I can think of two sources:
[1] http://discourse.soylent.me/ -- Plenty of people on the discussion boards
[2] http://www.youtube.com/watch?v=I8WpksPED_Q -- Week long study
As of now it hasn't existed for more than a few months so it's a little hard to give sources for trying it for "years".
Additionally, Rob strongly suggests NOT eating it every day.
As for problems arising months (or years), there's also a post about that too: http://robrhinehart.com/?p=570
