Yeah, and their configuration is mostly automatic; running the tasks starts their respective server and injects the client-side code to connect to them in the build.

boot-reload will hot reload new code on file changes, and optionally run a client-side hook. I use it to remount my react views. boot-cljs-repl provides a REPL into the browser you can use from the cmd line or directly in your editor. I'm using it with emacs-cider, but there are clients for most major editors.