When I created rur-ple, my intention was to use it to teach my pre-teens computer programming. When it was working reasonably well, and after having written a few lessons, I showed it to my daughter who quickly went through the material I had prepared and concluded that it was too easy/boring. She essentially decided then that programming was not for her.
Fast forward 10 years. She had to do some programming as part of her university program and found out that she really enjoyed it. She is currently more than 1000 km away, working in a lab where she has to program in Python, which she is essentially just learning. She had a question for me, emailed me some code when I got the idea of using Reeborg's world's editor and the embedded TogetherJS from Mozilla so that we could share a screen, while talking using Skype.
The only limitation that we found is having the TogetherJS chat window in a fixed position. If it could easily be moved (on a per-user basis), it would make it even more useful.