While Aquamacs is a viable choice, from what I understand Aquamacs is not fully compatible with the Gnu Emacs settings and I was advised by people I trust that Emacs.app was a safer bet. I tried Aquamacs anyways but can't say I liked it very much. Emacs.app with @technomancy's Emacs starter kit made things pretty easy.

I also tried Emacs.app and Aquamacs. Aquamac's behavior was totally odd & didn't match any of the documentation. I found the Cocca Emacs.app to be much easier to set up and get running. That said, neither of them feel as good as MacVim, as far as native Mac apps go.

I used the following version of Emacs back when I had a Mac.

http://emacsformacosx.com/

How so?

Lots of little things.

The one that drives me really crazy is that on Lion, both Emacs freak out if you try to resize from from anywhere except the bottom right corner. Similar issues with the green (+) button; full screen mode, etc.

Also, since you'll probably remap cmd to meta, you lose some system shortcuts which can be convenient when switching back and forth between various apps and your brain can't keep all the shortcuts straight.

those don't seem specific to aquamacs. I also don't remap cmd to meta, i bind the most common things to cmd like this.

(global-set-key (kbd "A-j") 'find-file)

I was referring to "neither of them feel as good as MacVim" - in particular with the Lion resize issues

I'm not sure what the value of emacs purity is. I've used both, and I like aquatics better. Either way, the setup for clojure is effectively the same.

For one thing, if you work on other platforms you might want Emacs to behave the same way on all of them.