I've been a powder user since 1.6 so I only have those products to compare to. First, I liked 1.7 more than 1.6. I compared them side by side and found that 1.7 had a more neutral flavor and removed something that I can only describe as "artificial" tasting in 1.6. But they were rather similar in taste and texture. I liked them both and was a happy customer with both.
Now that we've moved on to 1.8, I think that there is a much bigger difference in taste and texture from 1.7 to 1.8 compared to 1.6 to 1.7. I personally don't like the taste of 1.8 as much. It has an aftertaste that is different that I'm not a big fan of. Kind of a "corn-like" flavor. Not enough to cause me to cancel my subscription but it just doesn't taste as good as 1.7. Totally subjective, I know. As far as texture, there is a little bit of grittiness to 1.8 that was not present in 1.7. I mix my Soylent in a Vitamix so it's not just a case of it not being blended properly. Again, not a deal breaker, but as a fan of 1.7, it is a step back for me.
I just started my first bag of 1.8 this morning so I don't have any feedback on digestion yet but in the 4 hours since I've eaten 1.8, no problems.