Fair question!

Grammar: kakoune is heavily oriented towards selections. Things that happen in normal mode operate on the current selection. It's like using visual mode in Vim, except it's always on. It takes a little getting used to, since any cursor move changes the current selection. Part of its selection orientation is excellent support for multiple cursors.

Platforms: POSIX only. No support for odd platforms. If you want to use it on Windows, you have to use Cygwin.

Packaging: basically non-existant. You pull it from github and build it yourself.

Maturity: kakoune doesn't have version numbers as far as I can tell. I've had it crash on me, but it's rare.

Community: tiny but vibrant. There's #kakoune on freenode, which the core team seems to monitor pretty actively.

Syntax highlighting: yes, and it's more flexible than vim's. You can use it to roll your own colorcolumn, for instance.

Code folding and line wrap: these aren't there in kak, and I do miss them, but not enough to go back to vim

Tmux integration: awesome in kak, absent in vim. One of my new favorite things. In general, you can have multiple editors attached to the same session.

Automation / configuration: There's no such thing as kakscript, which I see as a plus. Nevertheless, you can do a lot of stuff here; I haven't scratched the surface, but there are lots of interesting example kakrc files out there.

Two main differences for who comes from vim in my opinion:

1) Editing model based on (multiple) selections. Instead of moving around and issuing verbs on objects, as in vim, you are always selecting something and the command (delete, change, yank and so on) comes afterwards.

It may not seem very different from vim, but the huge advantage is the feedback that you get from the editor.

2) Scripting kakoune is totally different from scripting vim and somewhat harder. If you need something in vim, you write your vim script and that's it. You can't do this in kakoune because the editor language is not a programming language, but only allows you to communicate with the system.

This is the reason why POSIX is a hard dependency, every script in kakoune usually relies on POSIX binutils to do things.

I've been learning to use UNIX more since I've started to use kakoune.

If your interested in text editors then it's worth watching some youtube videos on kakoune. There are some great ideas in there that even the old dogs could learn from. Actually, a lot of us could learn from it when it comes to things like feature discovery, it's a really good example of complex yet easy to use software.

The reason I haven't switched is because I prefer vims command->motion over kakounes motion-command, which doesn't quite sit well with me and because I don't like the scripting choices they made.

my take: the main strength and weakness is that kakoune is visual mode by default, so you see the effect of your text object commands without guessing (c3fx? c4fx?). having something always highlighted can be annoying.