Gorp is not a new idea. In fact you can get it for free in every single hiker box on the AT. I know someone who claims he didn't buy a single meal on the trail.
The disadvantages to soylent are taste, chewing difficulty/calories, preparation, it stops up your digestive tract, and takes much longer to become usable energy.
Trail mix (never heard the word gorp before) is nothing new, neither is muesli. My version above, however, is low sugar and a complete protein with much more varied nutrition sources. Thought it doesnt taste quite as good to your sweet tooth as a bag of m&ms and nuts.
The disadvantages to soylent are taste, chewing difficulty/calories, preparation, it stops up your digestive tract, and takes much longer to become usable energy.