Quoted: Alice & Bob talk DVCS.

Very handy. Mutable changesets via named patches, can be easily versioned independently (thus, cloned and pushed and pulled) without cluttering up the changelog (via qcommit/qci). With Mercurial, you can truly have your cake and eat it too.

Quoted: This extension allows you to transplant patches from another branch or repository.
It records the original changeset ID in the transplanted changeset, and avoids transplanting previously-transplanted patches.
It can also be used to rebase a branch against upstream changes (including dropping changesets that have been adopted upstream), to rewrite changesets and to cherrypick some changesets.