Eric S. Raymond has apparently begun work on a new version of Emacs' built-in version control (VC) mode which addresses one of VC's historical shortcomings: its file-centric model. VC was originally designed for RCS, which tracks each file individually.
"NewVC" now has the basic infrastructure to manipulate changesets for backends that support them (Subversion, Arch, Bazaar, Mercurial); there's no UI yet but it looks promising... This change was long overdue, committing several files in one go is a must-have nowadays even with less advanced tools like CVS and having a common framework can only be good. Over the years, a number of more advanced interfaces like PCL-CVS and psvn.el have been developed to compensate for VC's defects, all with subtly different keybindings, which makes for a rather annoying experience.
I bet the folks over at DVC aren't too pleased though, since NewVC will probably make DVC mostly irrelevant.