I use this in combination with `use-package`.

Here's the relevant section copied from my config, copied from right at the top:

  ;; Straight bootstrap
  (defvar bootstrap-version)
  (let ((bootstrap-file
         (expand-file-name "straight/repos/straight.el/bootstrap.el" user-emacs-directory))
        (bootstrap-version 5))
    (unless (file-exists-p bootstrap-file)
      (with-current-buffer
          (url-retrieve-synchronously
           "https://raw.githubusercontent.com/raxod502/straight.el/develop/install.el"
           'silent 'inhibit-cookies)
        (goto-char (point-max))
        (eval-print-last-sexp)))
    (load bootstrap-file nil 'nomessage))

  ;; Set up use-package for tidier package configuration/installation
  (straight-use-package 'use-package)
  (setq straight-use-package-by-default t)

  ;; Add diminish, which makes it easier to customize lighters (minor mode display)
  (use-package diminish)

I use it since it allows for transparent installations, meaning you can find the straight folder (in my case "~/.config/emacs/straight/repos/") and see git repos for all of your installed packages. From there you can edit them, commit to upstream, pull, all of the usual stuff.

Another main reason to use it is that it allows for repeatable installations, something I had struggled with previously with `package.el`. Run `M-x straight-freeze-versions`, and you have a lock file made with the exact commits of all of the dependencies you're running. That way, you don't need to push your entire emacs config folder up to your dotfiles repo, and can get a new install of emacs set up feature-(and bug)-exact on new machines easily.

One gripe I have about it though is that flycheck no longer recognizes `use-package` syntax in my init file and throws a bunch of warnings as a result. If anyone knows a quick fix, please let me know!