So Bill de hÓra says that IDEs don't matter, where the version control system has a first order effect on software.

I disagree.  I'm more productive with a good IDE than with a bad one, and far more so than with no IDE. 

If you come from a world where you haven't had a good IDE to work with, then maybe that statement is true; but I don't know anyone who's worked on a large project that's set up to integrate well with Visual Studio or Eclipse (and I'm not talking about "edit in the IDE and then run the external build tool to build here) who would give up using an IDE.

If what he's saying is that your choice of IDE doesn't matter, well, there could be some truth to that - but most platforms have one or two dominant IDEs that really do the job well.  XCode on the Mac, VS for Windows, Eclipse and IntelliJ for Java.  There aren't many bad choices.

On the other hand, I've used some bad bug tracking systems and bad version control systems.  Picking the right one is more important when the options include bad ones.