As a Clojure (and Java) dev, I started with Cursive and eventually moved to emacs w/CIDER as I became more comfortable with it. Cursive is great for people new to the language who may not know emacs - learning a new language is challenging enough without also having to constantly refer to an emacs cheat sheet :).
FWIW Cursive is also great for people who have a lot of experience with Emacs and just can't be bothered with it. Popular examples include David Nolen and Timothy Baldridge (and me), but there are plenty more too.
One representative comment that someone made to me at a conference was along the lines of "Since my boss encouraged us to move to Emacs, I've never spent so long fiddling with and arguing about my editor config. After a while most of us moved to Cursive and all that just went away".
I think Emacs is generally easier to get along with these days, but it'll never be as easy to use as a "normal" app where things just work out of the box. Some people like that, and others don't, but it's not as simple as a division between newbies and experienced users. They're roughly equivalent in power these days, some things Emacs does better and others Cursive does better - fortunately there's plenty of room for both, even in a userbase as small as Clojure's.
