I've been on openSUSE for 10+ years, and it is truly the gift that keeps on giving. The community super knowledgeable and responsive, and the distro is stable.

The biggest advantage openSUSE has compared to other mainline distributions is the openSUSE Build service (OBS). Contributing patches to existing packages is simple, and the build service also hosts custom packages in a personal rep - this let's me keep any custom packages up to date across all my systems. I believe it works with other distros as well so you don't even need to use openSUSE to utilise the service