I work professionally with Ruby and .NET. The current project I'm working in is written in Ruby; the project before that was written in C# 3.5. I use Intellise

I work professionally with Ruby and .NET. The current project I'm working in is written in Ruby; the project before that was written in C# 3.5. I use Intellisense a lot in C#, but oddly I don't miss it when I'm programming in Ruby. And when I'm programming in Clojure, I do have "Intellisense" via SLIME, but I don't actually use it a lot. I'm not entirely sure why this is the case, but I'd speculate that it's because the REPL takes the place of Intellisense. In C#, I use Intellisense to remind me how a library works, and to explore the API. In a language like Ruby or Clojure, I have a REPL permanently open, and I use that for exploring the API, or reminding me how something works. It takes a couple more key presses to get to than the Ctrl-Space of Intellisense, but the REPL is more powerful. Also, modern REPLs usually support tab completion, so you can use it like Intellisense. Come to think of it, I use the SLIME REPL so often I should probably add an explicit keybinding for it.