It's simpler to write efficient low-level code in C, but you have to pay the cost of efficiency (in effort, clarity, and LOC) everywhere in your program, in every single function you write. For some kinds of programming, such as kernel coding, almost all of your code needs to be as efficient as you can make it, so that's fine. For a lot of application programming, though, low-level efficiency only matters for a small percentage of the code, so it's a good trade-off to use a more elegant and expressive language, if optimizing the performance-sensitive parts isn't so difficult that it cancels out the savings elsewhere.
That caveat makes analyses like this one interesting, because the trade-off hinges on how hard it is to write efficient code when you need to. For me, the significance of this article is that it's possible to write high-performance Haskell in a simple and readable style if you're a Haskell expert who knows a lot about how the compiler optimizes code. That's a useful thing to know if you're considering using Haskell for a project. (The next thing I would ask is whether you're screwed if you're just an intermediate programmer who knows the language but not the implementation.)
Not to take away from Haskell, but this is exactly why many people in academia use Python. It's easy to express an idea in it, and test at a low performing level. Then when you know where your bottle necks are, you can re-write that tiny bit in Cython and gain 90% of the speed improvement of writing the whole thing in C.
That caveat makes analyses like this one interesting, because the trade-off hinges on how hard it is to write efficient code when you need to. For me, the significance of this article is that it's possible to write high-performance Haskell in a simple and readable style if you're a Haskell expert who knows a lot about how the compiler optimizes code. That's a useful thing to know if you're considering using Haskell for a project. (The next thing I would ask is whether you're screwed if you're just an intermediate programmer who knows the language but not the implementation.)