A few things... agree with Wes on the terminal launch for handling the java install.
Also, Safari is ubiquitous on OS X, and I only keep Chrome around for Mega downloads... would be nice if we could have a Safari-friendly d/l for beginners.
I changed the default install location to /applications, which then of course dumped half-a-dozen different folders in my main apps folder. Not very Mac-like. Not a big deal, but I had to go back and do the default install of /applications/nxt. Would be great if we could have a monolithic Mac app that had package contents (not sure if that's possible with your cross-platform installer).
Strictly from a simple end user's perspective (someone like my Dad). I wouldn't use this. I open up my /nxt folder, and I see 32 separate files, with no apparent or obvious app/launcher ("hey, click ME, I'm the icon that fires up the Mac NXT Wallet!").
I open up the read me, and there's nothing on the Mac install. Nada. Just Linux and Windows.
I appreciate the effort for a single, unified installer. It's definitely needed. But for the Mac, we need something like Bitcoin Core -- a single icon that launches an app. Can I use what was installed? Sure, *I* can, but can other users? Way too complicated imho.
For now, I'll stick with PoofKnuckle's solution -- much more elegant and simple.