I've owned the S4 for over a year. When it comes to mixing you may have to manually adjust the beatgrid for DnB tracks, but it's a small price to pay for such great flexibility and potential.
The S4 also bonds well with Logic. Just set the controller to "Midi Mode" in Preferences and then map away. And if you want to use the headphone output of the S4, I believe you switch the output from 1-2 to 3-4 on the master.