We all know the caveats on http://shootout.alioth.debian.org/u32/which-programming-lang... , but I would point out over the last few years, more and more languages are creeping up into the < 3x range on C. Go and Haskell I have some hopes that within a year or two they may well show up in < 2x, Scala's there, and Mono's putting up credible numbers in C# and F#. Given how much even "performance critical" code is still IO-bound nowadays, and how much not-IO-bound code is moving to the GPU anyhow, the age of "We have to use C++ for the performance" should be rapidly coming to a close. The last bit missing is just the people bit, now.

I don't know what the first non-C practical OS will look like, but I hope I live to see it. I can't believe in 2011 my OS is still getting buffer overflows and memory mismanagement and all of the foibles that despite everyone loudly declaring is all the programmer's fault and not the langoage's fault, still seems to follow the language around like dog poo stuck on its shoe.