There are some aspects of document editing that can be distinctly unsatisfactory in tools like RStudio (say, search and replace). I often find myself juggling between the two, and making modifications with Geany when RStudio falls short, or when interaction isn't necessary.
The integration with the console is helpful for very simple and casual use cases, like wanting to quickly test out something. For instance I'm currently learning Python and I like testing out examples in Geany as the interface is intuitive and the setup incredibly easy. (By comparison, I tried Atom and couldn't figure out how to use it for interactive sessions in Python. Years back when I tried Eclipse for R it felt like an ergonomic horror story. It's likely just me though.)