Performance is a huge bullet point for me. A language such as Python or Ruby requires you to make considerations (writing performance-sensitive code by shelling out to a native C extension, for example) that don't crop up in a natively compiled language such as Go.
In fact, for performance-sensitive things the difference is often staggering, even for things that scripting languages were originally invented for, such as text processing. Performance-sensitive doesn't always mean "DSP or graphics code". If you want to process huge log files in Ruby, for example, you can start as many threads you like to attempt to parallelize it without getting anywhere because of the global interpreter lock, and will find yourself resorting to things like forking off child processes. Ruby would be a bad fit because it does not perform well. I often end up writing such processing code in Lua (using LuaJIT) because of the dramatic difference in performance.
One must always consider the domain, but performance is one important facet of Go: Go gives you high performance without sacrificing much of the expressiveness of dynamic languages such as Python and Ruby. (Conversely, C/C++ gives you high performance without the same expressiveness.) If Go had the same VM as Ruby I would probably never consider using it for anything, as I don't see any language-level benefits that outweigh the performance aspect.
In fact, for performance-sensitive things the difference is often staggering, even for things that scripting languages were originally invented for, such as text processing. Performance-sensitive doesn't always mean "DSP or graphics code". If you want to process huge log files in Ruby, for example, you can start as many threads you like to attempt to parallelize it without getting anywhere because of the global interpreter lock, and will find yourself resorting to things like forking off child processes. Ruby would be a bad fit because it does not perform well. I often end up writing such processing code in Lua (using LuaJIT) because of the dramatic difference in performance.
One must always consider the domain, but performance is one important facet of Go: Go gives you high performance without sacrificing much of the expressiveness of dynamic languages such as Python and Ruby. (Conversely, C/C++ gives you high performance without the same expressiveness.) If Go had the same VM as Ruby I would probably never consider using it for anything, as I don't see any language-level benefits that outweigh the performance aspect.