The Mercurial team has paid close attention to what has worked with competing packages in the past from a user interface perspective. Thus the learning curve is minimized so you can learn the tool separately from learning the internals of distributed version control management. In general, the user experience is very good, and if you know SVN you can get started right away, learning as you go. For this reason, even though I use git at some customer's locations, I use git or svn, Mercurial is my own tool of choice.

Mercurial is very powerful distributed VCS with very simple branching model. It is excellent for small projects with relatively short history as well as awesome for big enterprise level projects. One more "feature" of mercurial is it's mercurial-server - very simple and reliable way to organise private repository server.

Mercurial HG is what is called a distributed version control system (DVCS) that let you develop a repository completely offline. Basically when you clone a repository the full revision history is copied locally and you're enabled to add your own commits, even if your collaborators are working on their own clones. It has a syntax that is easier to remember compared to git and works flawlessly on all the major platforms.