A "next generation" Vim effort. Major overhaul to support more powerful plugins and better integration with tools such as IDEs.
Ranked in these QuestionsQuestion Ranking
Pro Still Vim but with upgraded features and some issues fixed
NeoVim was a complete rewrite of Vim, with new features added and underlying issues resolved thanks to the Vim code base. The keybindings and configuration are the same as Vim, so the switch can be pretty simple.
Pro Built-in terminal emulator
This avoids the user having to make any installations.
Pro Better integration with external tools
The core text editor is "headless", meaning it's detached from the user-interface so other programs can hook into it. This enables better integration with IDEs and browsers, where "Vim mode" has typically been a poor substitute because it was a partial rewrite or a partial port at best. One of the advantages of Vim has always been ubiquity and Neovim makes it even more ubiquitous.
Pro Modern code base
As a refactor over Vim, Neovim has greatly improved its code base. For example, some functionality is handled by libuv, the same code base that powers Node.js.
Pro Powerful plugin model
Vim plugins have always been useful, but tied to specific languages. Neovim's architecture provides better separation between plugins and the core product, so that plugins are completely flexible and can be written in any language.
Pro UI Agnostic
The core functionality is handled apart from the UI, meaning that Neovim can be embedded into any other GUI system, such as Atom.
Con No graphical editor yet
At the time of writing this, no equivalents to gVim exist.
Con Limited cross platform support
Neovim is not yet available on Windows (nor other legacy platforms).
Con Why clone Vim
You can use Vim and plugins.
Con No stable release yet
As of yet, Neovim is in an unstable point in it's development. There is no stable release and using it for the moment should be done with caution as many features may change in the future.