I've never had a Nikon camera break, so I personally wouldn't worry about reliability, whether it's a mechanical camera or a fully electronic one.
You can put Leica R lenses on a Nikon camera, as well as Nikon lenses. Other than T mount lenses, I think that Leica R cameras only work w/ Leica R lenses, if that makes any difference. A few people did make R mount third party lenses, but the Leica R lens system is outstanding for image quality and workmanship.
I once had a tiny Nikon FG w/ a Leica R 90 Summicon on it, that was a fun and light package.