Well, if you're talking GUI stuff, nothing in Nim compares to Qt. But, I did routinely use Qt for console, server, and headless embedded stuff. The Qt environment compensated for lots of C++ shortcomings up to recently. I think I've seen a Nim linkage to QML (Qt's newer Javascript UI markup language). But, I've never been all that keen on it. Depends what you need in a GUI. QML worked well for me on android/ios apps. I guess I'm just old school when it comes to desktop apps, and I can bang out a Qt gui app in a hurry for the desktop. A few times, in D, I'd written all of the logic for the application in D as a console app with a command handler that worked on stdin that would generate the same Qt data model on stdout that a Qt GUI app would use to populate its model-bound tables and whatnot. Worked surprisingly well.
But, to end this treatise on the state of nim gui stuff... I've had some fun with nimx, but keep trying the more native stuff. give 'em a try.