I work for a small-to-medium-sized Rails shop (~12 developers capable in Rails, although many are full-stack, including myself) and many/most of us use Vim on a daily basis (should be noted, with heavy extension use). Those that don't mostly use Sublime Text, and our single emacs user is in the process of transitioning to Vim. Even one of our Objective-C colleagues managed to get Vim running hosted in Xcode somehow as an experiment. The support in the Vim community for Ruby and Rails-ecosystem languages and patterns (Coffeescript, Sass, Slim, Haml, and the like) is fairly good, and there's a number of IDE-ish features available as extensions. I've been pretty satisfied with it since moving to the Rails community, although I'll admit my background wasn't heavily into IDEs at all, and the only full Ruby-focused IDE I've seen, Rubymine, seemed intolerably slow and unusable.