"Write in Python/Ruby/whatever and optimize the slow parts in C" echoes around the programming community endlessly, but I wonder how many people have actually done it. It's kind of hard.

- Automated tools like SWIG have weird limitations and are complex.

- Binding to a C library manually means you have to wrangle the data from a heapy, pointery dynamic language world into whatever format the C libary wants.

- Writing the C code to operate on the dynamic language's objects directly means you have to learn how the language works under the hood, and your C code will never be useful in any other language.

- Python and Ruby both have a GIL that prevents you from using multithreading to its full potential.

- The way dynamic languages lay out objects in memory causes an inherent slowness everywhere. Your app's slowness may well be a death of a thousand cuts, with no easily optimized hot spot.

I think anyone who has actually worked on a project built this way will appreciate the idea of a compiled language that is closer to the expressiveness of Python.