Same here. No problem at all if a command I run once a week per project takes a few seconds. I can't imagine coding in clojure without leiningen. It stops me from having to deal with a tonne of complexity I really don't want to think about.

As for cljsbuild, I'm guessing this is more a clojurescript compiler issue since again, I run leiningen once and leave it to recompile on file change in the background. Yes would be nice to have some compiler speed improvements but really it isn't that bad. I wait a second or two, not tens of seconds. At least, this is the case for me but then my cljs projects tend too be a couple of thousand lines at most.