I'm an iOS developer and I mostly love iOS design and user experience but one OS that, imo, is better is MeeGo.

I used the N9 briefly for 3 months back in '12 or '13 and other than the ecosystem issue, the OS was intuitive and simple to use.

That being said, I'm slowly moving onwards to React Native projects so hopefully in the near future, my paths will re-intertwine again.