"I'd argue that auto-complete, one of the major IDE/editor features, is alone responsible for most of the boost I get from coding in an environment. Instantly, thousands of symbols can move out of my brain and into a list that appears as I type."

This is exactly what I had in mind reading this article. My experience with IDEs and languages has been that they are, for the developer, orthogonal to one another. Throughout school I never even touched an IDE - ended up writing a 100KLOC+ program (C compiler) with a text editor and debugging using print statements, no debugger or anything. It was a ball of mud but it worked great.

Where IDEs have really helped me is for larger scale projects, especially where I integrate lots of new-to-me 3rd party libraries. Being able to contextually explore the namespace of the libraries without sorting through all the documentation is a huge time-saver. Refactoring is also a plus; I don't end up using the refactoring tools that often but Eclipse's refactoring beats find-replace any day.

I guess what I'm trying to say is, languages help developers implement algorithms and data structures. These tend to be the 2-by-4s and screws of software development; a high-quality language is a straight, square, well-finished set of building materials that are sized & shaped for the structure you're building. IDEs help explore namespace and refactor, they're your drills and saws. Understandably the building materials can influence how easy it is to work on them with high-powered tools, but from a development perspective, they're complements, not substitutes.