I feel that editor extensions for git are the future for 99% of git interactions. Git+[fugitive/etc] still may not be as slick a UX as Mercurial+[mercenary/etc] (I've not actually used any editor extension for mercurial) but it really comes close to closing the gap. To the extent the UX advantages of Mercurial really seem very marginal to me.

But when it comes to Fossil, nothing I've seen comes close. It's built on sqlite which I think turns off a lot of people who have prejudices against SQL, but sqlite is the furthest thing from a big 'enterprisey' RDBMS that give most users the shivers. It's a really tight piece of software, and in fact Fossil is created by the creators of sqlite and the sqlite project is managed with Fossil. So fossil's vanguard project (sqlite) has more deployments than even git's vanguard project (linux)! Mercurial has Firefox and Python, nothing to sneeze at; clearly it's a capable VCS, but I guess my point here is that Fossil doesn't get the attention it deserves whenever people talk about a FOSS alternative to git.