We (at repl.it) discovered remi when we were looking for a native GUI alternative. Found remi and was able to write a TicTacToe game in 30 minutes, it felt natural and the app is fast enough to not notice it's remote. Take a look (source code there too):
https://repl.it/talk/share/Python-GUI-Tic-Tac-Toe/6145 (might not take the HN load tho)
The reason we started looking into it is that we have a lot of users wanting[1] to write GUI apps and although we support all the major Python web frameworks[2], users, especially novices, still find it easier to write native GUIs. And I can't blame them, after you've learned a bit of Python, learning to write web apps is a whole new ballgame (HTML and CSS are a different style of code altogether that warps people's minds at first).
Here is a basic demo that renders a plot (using matplotlib) if you want to fork and play around with it: https://repl.it/@amasad/remi-repl-demo