[jkn]

You're right of course about the GC metrics. And there was some disappointing increase of GC CPU usage with the 1.8 changes (I don't now the current status). But some of the items you mention (package management, mature optimization framework) will hardly make cases where Go cannot be used, which was the original point. Same for concurrent data structures which can be implemented in Go, even if the lack of generics makes it less convenient. I do agree with you regarding the other items.

[pcwalton]

Aggressive compiler optimizations are not optional in many domains.

One rule of thumb that a lot of people don't realize is that if you aren't maxing out your sequential performance, your parallel multicore algorithm usually loses to an optimized sequential one. The reason is simple: parallelism introduces overhead, leading to guaranteed sublinear speedups. Compiler optimizations, on the other hand, frequently result in multiple factors of improvement.