[ubernostrum]

"And this requirement to test the shit out of your code [2-to-1 ratios aren't uncommon] kills the spirit of exploratory programming for me."

Which is why most of us don't write unit tests when we're in the exploratory phase of something.

"Moreover, 200x speed penalty means that simple O(n) algorithms won't cut it for an average data set, forcing you to build more complex solutions just because your language can't scan a big-ass array under 10ms."

I think that you and I have different ideas of what an "average" data set is, then, or the performance constraints expected of it. Although given the number of mathematicians and professional scientists who crunch their data in Python these days (see: NumPy, SciPy), I'd also suspect that maybe you should investigate this a bit more deeply.