I really like Repl.it as a learning tool, and I used it a bunch while transitioning from ruby to python, although its also given me a few bad habits, and I've never been able to find much use for it while working on "real" projects. Still, I pull it up from time to time, just to confirm some bit of code I'm working on.

it's still the best multi-language Powershell ISE-ish repl I've ever used though :)