I also didn't care for the OEM; but am hesitant to replace the shifter left I void my warranty (call me paranoid). Last week, I upgraded the shift knob to a Steeda whie cue ball shifter from LateModelRestoration. It didn't do anything in terms of performance but it feels much better in my hand - For now, I think I'm going to keep the rest of the shifter as-is.
By the way, love the wheels - I have the same on my '13 black GT. Personally, I think they're the best set available on the current Mustang; though it's a pitty they won't clear the Brembo calipers (or so I've heard/read)
2013 Mustang GT Premium
-MT82, 3.31, 19" rims. Completely stock (for now)