> I don't doubt that you can write productive systems in CL (bit of a fan myself), but the "oh we have smart compilers that just make it as fast as C" just isn't true.

But 50% of C is great. Imagine in Lisp you can achieve 50% performance of C. That means you can write large amounts of your code in Lisp, without the need to use C.

Actually it is both better and worse. One can achieve better than 50% and in many cases one is slower than 50% of C. For example you can optimize your code at runtime using the Lisp compiler. But in many cases you will be slower, since C compilers and libraries tend to have better support for hardware.

For many many applications 50% performance of C is completely sufficient. Zillions of lines of code are written in much slower environments...