You know how when using git you have to add tons of flags to every command to make it do what a sane person would actually want? Mercurial just does what you want.
I have used (actually introduced) Mercurial before at a company and considered them basically equivalent enough, only to get stuck in some horrible design choices of early Mercurial (named branches and not having rebase by default). I am happy to see these elements corrected in Sapling, giving me enough confidence that I might actually use Sapling over time...