This is my new favorite version control system.
I personally like to develop under the cover of a version control system. I don’t consider professional development to be occurring unless one is being used.
Hg is great for quick refactoring developments. It’s a distributed vcs (like git) so that the application does not enforce a centralised server.
This means that you can commit multiple changes to your local repository before pushing these up to the shared server.
You can also push changesets from developer to developer without going via a central server!
This is wonderful for collaborative development or for those developers who code on the train or plane!
This neatly solves the problems that the PVCS promotion model handles (i.e. how to check in changes without breaking the tested build).
Since you can freely clone a repository refactoring becomes a breeze.
Clone then hack away (checking in whenever it actually compiles and runs the tests). The cloned repository can be thrown away or merged back into the master (or just your current working copy).