This is a temporary regression. I guess generics would be a permanent slow-down, and might not scale nicely for larger projects - although I do now know enough about the workings of compiler algorithms to judge that.
I don't think generics would result in a compile time slowdown relative to the alternatives. If you don't have generics, programmers work around it with code duplication or they work around it with dynamic typing (interface{}, but also the runtime support for maps and channels fall into this category). Not coincidentally, these are the two main ways to implement generics in a compiler.
