“cutting-edge” feels a bit empty to me.
Let’s see:
“Haskell: where stability meets evolution. A language that grows with you.”
I think this is actually a bit sharper, because “evolution” relates to the second sentence.
It’s fairly vague, but I haven’t seen any other language front page word it this way. It’s a good way to stand out. We’d probably have to explain somewhere what we mean by this, e.g. in the “Why Haskell?” section:
Stability meets Evolution
Build powerful abstractions via latest functional programming principles. While Haskell’s core is rock stable, the language is constantly evolving, but does so through rigorous processes. Learn new tricks and features as you go, while relying on a solid foundation.