I got it running on El Capitan without using XAMPP. I used Apache that comes with Mac OS X, installed PHP 5.6 and MySQL 5.6. I have a pretty decent iMac/Macbook Pro and M2 is still really slow when set on developer mode, almost unusable but this is mostly if you will be doing theme development. Its slow when the server has to recompile everything.
Here is some links I used to setup Apache/PHP/MySQL:
PHP 5.6: http://php-osx.liip.ch/