I've been using Soylent off and on for about 7 months now. It's awesome except for the taste. The health effects are almost instantaneous. After a few weeks, I didn't just feel healthier, I felt more alert, better rested, and more cheerful. My INTJ noticed the same (though we kept it to ourselves at first because we were both afraid of sounding like fruitcakes).
I started out eating/drinking nothing but Soylent and water, but after about a month, I was having hot, meaty cravings. I've stuck a balance now where on weekdays, I eat Soylent for breakfast and lunch, and have a dinner. On the weekends, I only have Soylent for lunch. My INTJ does the same.
The best thing I've found for the taste is chocolate syrup or fresh raspberries.
Also, ALWAYS USE A BLENDER TO MIX IT! It says you can mix by shaking and it's lying to you. Any chunkiness left behind is likely to make you gag, especially at first. Also, I wouldn't advise trying it without masking the flavor. Over time, you'll get more used to the flavor and can live without supplementation, but even if it's a sugar-free coffee syrup, you need something to mask the waffle-batter taste.
One more thing -- thin it down a little (not a lot) more than instructed. And make sure it's really cold. I make it the night before so it's as cold as possible when I drink it.
Edit:
I use v1.5
I can't afford the premixed kind. The powder comes out to be the same price as healthy (not ramen) groceries for me, so that's what I use.