This largely depends in the IDE. The thing is, that a language like Nim is 'competing' with other languages like Java, C# or Python where interactive debugging is a given. I would highly prefer a language which compiles down to C code, but it's hard to give up an IDE like Visual Studio or Eclipse.

I know that many strong developers do not care that much about debugging or can use GDB without thinking. But unfortunately I'm not one of them. And I fear that Nim will stay a niche language because of that..