Last time I looked into 'git notes' it wouldn't preserve the notes attached to a commit when you amend / rebase / cherry-pick the commit. It seems that git now supports this! From the git-notes manpage:
notes.rewrite.<command>
When rewriting commits with <command> (currently amend or rebase),
if this variable is false, git will not copy notes from the original
to the rewritten commit. Defaults to true.
I'm using git notes to annotate my commits with metadata about what bugs they fix, how stable they've proven to be in practice, and the dependencies between commits: https://rwmj.wordpress.com/2011/03/28/half-baked-ideas-class...