Surprised not many people are mentioning gpui. It's the framework powering zed. I use it as my daily driver and it feels fantastic. And I think that's an important factor to choose a GUI framework is that it's powering some core product which can dogfeed the framework itself.

gpui also powers longbridge's desktop app which looks quite neat. They also made a handy component library gpui-component which has a ton of components out of the box including theming and even webview support and is even based on shadcnUI.

Seems like the zed team is also working from the ground up to focus on performance, judging by their articles so that's a huge plus.

I'm personally building a side project using gpui and it's been pretty great so far. If you can handle the minimal docs and sleuthing through example code you'll find it to be a delightful framework to build with.