Recs.
Updated
Vim is a powerful, portable, keyboard based text editor. Being text-based, vim is lightning fast, with an incredible set of features developed over its multi decade existence.
SpecsUpdate
Pros
Pro Lightweight and fast
When compared to modern graphical editors like Atom and Brackets (which have underlying HTML5 engines, browsers, Node, etc.), Vim uses a sliver of the system's memory and it loads instantly, all the while delivering the same features. Vim is also faster than Emacs.
Pro Useful undo features
Vim does not only offer unlimited undo levels, later releases support an undo tree. It eventually gives the editor VCS-like features. You can undo the current file to any point in the past, even if a change was already undone again. Another neat feature is persistent undo, which enables to undo changes after the file was closed and reopened again.
Pro Flexible feature-set
Vim allows users to include many features found in IDEs and competing editors, but does not force them all on the user. This not only helps keep it lighter in weight than a lot of other options, but it also helps ensure that some unused features will not get in the way.
Pro Productivity enhancing modal paradigm
As with all vi-like editors, Vim provides a modal paradigm for text editing and processing that provides a rich syntax and semantic model for composing succinct, powerful commands. While this requires some initial investment in learning how it works in order to take full advantage of its capabilities, it rewards the user well in the long run. This modal interface paradigm also lends itself surprisingly well to many other types of applications that can be controlled by vi-like keybindings, such as browsers, image viewers, media players, network clients (for email and other communication media), and window managers. Even shells (including zsh, tcsh, mksh, and bash, among others) come with vi-like keybinding features that can greatly enhance user comfort and efficiency when the user is familiar with the vi modal editing paradigm.
Pro Has multiple distinct editing modes
Interaction with Vim is centered around several "modes", where purpose and keybindings differ in each.
Insert mode is for entering text. This mode most resembles traditional text entry in most editors.
Normal mode (the default) is entered by hitting ESC and converts all keybindings to center around movement within the file, search, pane selection, etc.
Command mode is entered by hitting ":" in Normal mode and allows you to execute Vim commands and scripts similar in fashion to a shell.
Visual mode is for selecting lines, blocks, and characters of code.
Those are the major modes, and several more exist depending on what one defines as a "mode" in Vim.
Pro Keyboard-based, mouse-free interface, and trackpad support
There's no need to reach for the mouse or the Ctrl/Alt buttons again. Everything is a mere key press or two away with almost 200 functions specifically for text editing. Vim does support the mouse, but it's designed so you don't have to use it for greater efficiency.
Versions of Vim, like gVim or MacVim, still allow you to use the mouse and familiar platform shortcuts. That can help ease the learning curve and you'll probably find you won't want to (or need to) use the mouse after a while.
Pro Extremely portable
Vi/vim exists on almost all Unix-like platforms. It's the de-facto Unix editor and is easily installed on Windows. All you need to make it work is a text-based connection, so it works well for remote machines with slow connections, or when you're too lazy to set up a VNC/Remote Desktop connection.
Cons
Con Doesn't play nice with the system cut/paste mechanisms
This can be worked around somewhat if you disable mouse for insert mode. You can then right-click your terminal and use paste like you would anywhere else in a terminal.
But it still doesn't feel right when the rest of your system uses Ctrl-C/Ctrl-V, and you have a system clipboard manager, and so forth.
Con Difficult learning curve
You'll spend a lot of time learning all the commands and modes supported in Vim. You'll then spend more time tuning settings to your needs. Although once it's tuned to your needs, you can take your .vimrc
to any machine you need and have the same experience across all your computers.
Con Poor support for external tooling
Many plugins depend on optional Python and Lua features, which may or may not be included in whatever binaries are available for your system. And without platform-specific hacks, it is difficult for plugins to operate in the background or use external tooling.