/me raising hand
I've used all the major IDEs on real projects for years at a time each, and so done years (often on the same projects) with just a quality editor and a set of external tools, and I honestly slightly prefer the latter.
I'm effective both ways, but my observation is that my work is of better quality when working in a non-IDE environment.
I fully understand that, as with most such things, says as much or more about me than about IDEs.
I think a large element is that, not having auto-complete, I find myself reading more docs (increasing system familiarity) and noticing unergonomic interfaces sooner.
The one feature I do miss is language aware navigation, but that loss is somewhat balanced by the lack of disruption when said navigation inevitably breaks, due to non-compiling code or working with new language features not yet supported by the tools.