From what I've read (I think in the most recent Ars Technica article on it, not counting today's 2.0 one), soylent has to sit for a while in the fridge after you make it or it's absolutely awful.
True. I'm on my first batch of 1.5 right now. The instructions are pretty clear about it needing to be cold. Room-temperature, the Soylent mix is pretty gnarly (think chalk), but once properly chilled it pretty much tastes like nothing.