Wanna quickly add a private .jar file / private repo? Good luck. Oh, it's doable, sure (I did it). But it's a major pain in the arse.
People will say: "But you shouldn't use free-floating .jars". Well, guess what... I like 100% reproducible builds that do not need to connect to Internet to be build. So now to have reproducible builds we need to have not only our DVCS but also our local Maven repository. Major major pain. I much prefer to have my jars managed by myself and commit them directly in the DVCS.
People will complain that it's not the correct to do it: but meanwhile I've got an easier time reproducing builds than they do...
During all my Java years (more than ten) I always managed to dodge Maven and the rare projects I inherited that were using Maven were utter mess. People will argue that it's because of people, like me, who don't know Maven well enough, that the entire projects (and builds) became utter junk. Whatever.
Another area where Leiningen/Maven really do not shine is when you don't have Internet access (like, you know, in companies which have separate networks, including ones non-connected to the big bag Internet).
Major major pain.
And what happens if you have an Internet connection but some high-target repo gets rooted and a major Java .jar gets replaced with a version containing an exploit?
Millions of devs account instantly owned by automagic Maven updates to your project.
It hasn't happened... Yet!
But lately we've seen enough Java exploits that one can reasonably think it's not "far fetched" to imagine that such a thing could happen.
Also I hate working in an environment which can change automagically, against my will. So I'm "staging" my development by using a dev account which has no Internet access and another one which does (it's easy to do on Linux, where you can trivially use per-user firewalling rules).
I've always been amazed at how many devs cannot correctly configure a Java classpath themselves and need to be babby-sitted by a tool like Maven.
As soon as I'll understand better how Clojure and how Clojure builds do work, I'll do just like I've always done with Java projects: custom scripts building from known good .jar files.
Not some magical tool constantly "phoning home" and being a security disaster waiting to happen...