Leiningen's goals are slightly different than clrj's. Leiningen is more like a Maven type project descriptor/build system whereas cljr is more like an easy_install-esque tool. cljr can be used without creating a project.
Yes, but it does have a repl command, and a swank plugin, and I like using it as a virtualenv-type tool even when I'm not working on a project. (And most of the time I am. I find the best way to learn is to attempt to write a real piece of software, and it has the added bonus that I might be able to add something to my portfolio.)
