The most interesting conclusions of Mike Pall reflect my experiences: sampling profilers are often much more usable in practice than instrumentation:

As you might have noticed, I had to change my plans compared to the original approach presented in June. The main problem with the instrumenting profiler was finding high-precision and high-speed timing sources for all platforms. (...) The necessary pipeline flushes shadowed the actual timings up to the point where the measurements were less accurate than with a sampling profiler! Other platforms offered only inaccurate timing sources or none that are accessible from user mode. And to top it off, the instrumentation added considerable overhead. (...) I had to scrap that work and decided to go with a sampling profiler.

And I don't know any other scripting language with a built-in sampling profiler. Does anybody?