Explaining why Smalltalk developers like their images is a hard experience to convey to someone who's accustomed to working with files. Here's a video I found that shows what it is to work on a running program.

He's demonstrating some of the features of the refactoring browser on a running instance of the classic Asteroids game. He extracts a method to a component, changes the color of the asteroids, then shows off undo and redo. He does so while the game is running without ever having to break his flow with something as silly as a compile, debug, run cycle that we've all grown so accustomed to in most other languages.

It doesn't matter how fancy modern refactoring browsers get, as long as they're still working on dead files instead of a live running program, they'll never be able to compete with Smalltalk when it comes to developer productivity and maintaining flow.