Having an interactive bash/ipython/repl session where you can use vim keys to navigate and yank lines from your scrollback is pure bliss.
I like to run builds and be able to see, yank, open files from the errors all inside vim.
You can do something like this with the :grep or :make commands with the resulting preview window. Even if you were to do something like :r !make, you can view the errors by moving your cursor to the file name and pressing ctrl-w ctrl-f (to open in a new split window) or ctrl-w gf (to open it in a new tab).
To be honest, I don't really like having a 'terminal' in vim. It makes more sense to just use the terminal, which is like, right there, one ctrl-z away.
- Vim is not a shell or an Operating System. You will not be able to run a shell inside Vim or use it to control a debugger. This should work the other way around: Use Vim as a component from a shell or in an IDE. A satirical way to say this: "Unlike Emacs, Vim does not attempt to include everything but the kitchen sink, but some people say that you can clean one with it. ;-)"
In summary, it took it so long to get it because it explicitly goes against the original design (and I kind of think it was the right choice. Emacs already exists).
1. I don't want to learn a bunch of new key bindings to switch between terminal and editor windows. With nvim, I can use the same process that I use to switch between buffers, to switch to a terminal window.
2. I can use the same process to copy to/from terminal/buffer windows, and use the full range of vim registers in the process.
3. I can name terminal buffers in the same way I name editor windows, and use the names to switch to the terminal window.
"In [terminal] mode all keys except <C-\><C-N> are sent to the underlying program. Use <C-\><C-N> to return to normal-mode."
:help terminal-emulator-input