(I was about to ask about the value of the time spent cooking, but it turns out he's already answered that.)
He has; for me, cooking is about three minutes of effort spread out over the course of fifteen minutes each day.
The main benefit to a Soylent-style diet is that you get all the micronutrients and so on that are normally locked away inside vegetables, which take an inordinate amount of time to prepare and consume, in one quick drinkable source, without any concerns about pesticides or fungi or so on.
Rob Rhinehart's food replacement Soylent now has a crowdfunding campaign.
If you're interested in one or more of these benefits, send in some money! There is also a new blog post.