1. I don't think powerful abstractions are often that useful. I use Python in my day job, and we mostly don't use many high level abstractions. We never use monads, for example, and while we do use async futures, these are strictly worse than Go's concurrency features.
2. Pretty sure abstraction power drives _less_ consistency, not more. Effectually, it means there are more ways to do the same thing (and more ways to screw it up and make a mess), and consistency depends on organization discipline and less on the rails of the language. I don't mean to say abstraction is bad--only that consistency is one of the costs, not an advantage.
I'm interested to hear your thoughts.