I've heard SSKs aren't great for your gear box, especially ones that really shorten the throw. The synchros can't match the speed fast enough so you get increased wear on your synchros, especially 2nd gear.
I've had the UUC SSK in my E46 for 40k miles and 3 years. Its held up very well, you do HAVE to properly torque the 6 bolt for the ERK mechanism. But I grind when I've got full throttle in first and then quickly shift to 2nd. I have to wait a quick moment before it will go in. Never had that issue with the OEM shifter with the same Royal Purple gearbox oil
2013 F30 328i Melbourne Red
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red