So far I am finding Soylent does not present major problems for cleanup. At first, it was a little annoying. Colder temperatures make it gluey, and that led to dribblling and occasional spots on clothing and nearby fabrics. But it is easy to wipe away the marks, even if they have been there for a while - Soylent does not appear to permanently stain anything. I usually clean the pitcher, scoop, and bottles the same as any other dishes - with sponges, brushes, and dish soap, and there does not seem to be any residue or odor left behind. I have noticed that the pitcher can take a long time to fully dry - water droplets seem to linger in it for some reason, but this is not a major issue. So thumbs up for cleanability imo.
Do you leave it upside down or right side up