I greatly prefer it, although if postman doesn't have any annoyances for you, then insomnia might not be better for your use case.
Mostly the environments & variables make insomnia pretty fantastic.
How do its environments and variables differ from postman?
It isn't dependent on your browser, which has made testing much more reliable in my use cases. My workplace uses a lot of single-sign-on stuff which makes it hard to authenticate using service accounts and whatnot.
When you tried Postman were you using the web app version (eg, in the Chrome store) or the native version (eg, in the Mac App Store)?
I wasn't aware it had a desktop app!
I wasn't either for a long time, and the desktop app has been much smoother in my experience.
Yes, recently noticed that I had some file upload issues with browser-based postman, and they suddenly disappeared when using the standalone. Not sure why, same settings. Looked like the browser based couldn't get the file/form encoding right.
It loads much faster, which matters a great deal to me.