ClojureScript, along with Reagent (or some other React.js wrapper like Om or Quiescent - I currently prefer Reagent, which has been gaining lots of traction recently), Figwheel and a browser REPL, has really had a lot of impact on how I view GUI development.
I do Winforms development in my day job and I hate it. The feedback loop I have from changing something in the code to viewing it in the application can be a matter of 1-2 minutes (need to compile, start up, login, setup everything to the correct state, etc). Going from that to being able to grow the application in real-time, without ever having to restart/refresh, is amazing, and makes me feel infinitely more productive. Combining it with Cordova to make mobile web apps, where I can deploy once to my phone and then have changes be applied over wifi as I type them into my text editor, is super sweet.
I do Winforms development in my day job and I hate it. The feedback loop I have from changing something in the code to viewing it in the application can be a matter of 1-2 minutes (need to compile, start up, login, setup everything to the correct state, etc). Going from that to being able to grow the application in real-time, without ever having to restart/refresh, is amazing, and makes me feel infinitely more productive. Combining it with Cordova to make mobile web apps, where I can deploy once to my phone and then have changes be applied over wifi as I type them into my text editor, is super sweet.
Getting everything set up can be a bit tricky, but https://github.com/plexus/chestnut makes it a whole lot easier.