I celebrate trying this. The last time that there was serious attempt at this was Smalltalk and it had a great impact on the industry. Itself a great balance of friendly instant feedback and great control. There is also Apple's Playgrounds now with Swift trying more or less on this. Definitively the instant feedback is a key component in having the right introduction to computing. If we extend this idea we'll find that we need this in the debugger too. It works because is the best way to replace imagination and assumptions with perceptions.