I plan to try it this summer for backpacking. While I drink it on a regular basis, I have yet to try it backpacking. Four main concerns I have are that
(1) it tastes better cold,
(2) it tastes better after sitting overnight,
(3) mixes best with hot water, and
(4) it is low in sodium.
The first three make a fridge a must for a regular soylent drinker. Alas, the super-lightweight backpacking fridge is yet to be invented. On the other hand, the most recent soylent formula tastes better and may be okay sans fridge. I have tasted it warm without being repelled. The true test would be drinking warm soylent all day, and I plan to try it this summer.
Low sodium may be a concern if one is planning on heavy exercise, e.g., many backpacking trips. Salty snacks can easily fill this void, which is what I plan to do.
On the plus side, the new formula (v1.4) does not need a separate oil bottle. It is just powder, which makes packing it a breeze. Also, the new formula has more fats and less protein than previous versions, which makes gas much less of an issue, at least for me. Your mileage may vary.
Probably the biggest pull for me is that one of the main energy sources in soylent is a carb that has a low glycemic index. It is great for endurance, fitting perfectly in with backpacking.