After re-installing MacOS from scratch, I found that I was having problems launching Arduino. I got the following error:
In order to solve this, I followed the instructions at rancidbacon.com. The solution was to use Finder to configure the application to launch in 32-bit mode. I quickly looked to see if I could modify the Info.plist file to enforce this behavior, but I don't see any way to do that.
Another solution from technobabble is to replace the library inside the Arduino app bundle with a 1.6 compatible version.