For people familiar with java, the jvm is an upside. Being able to use libraries (especially client ones) from your project can be very useful. The amazing interop support is very nice if your pragmatic over purist and don't plan on rewriting a ton of things.
This is true, if you're a java/jvm person, this is a huge upside, even if you aren't, once you see just how much code has been written in java, you'll probably come to appreciate the pragmatism.
When I learned clojure two years ago, I didn't have any experience with java or the jvm, so I had to sort of learn where the boundary was.
After that initial hurdle however, I now use java interop quite a bit.
