I was previously running these hubs with a Shimano XTR rear derailleur with XT shifters. Shifting performance was great, but my main complaint was that any time I hit any bumps at all, it sounded like my drivetrain was breaking off. Enter the SRAM Type-2 rear derailleur.
SRAM claims the Type-2 derailleurs deliver maximum drivetrain stability—even through the most punishing technical terrain. Through the use of a Roller Bearing Clutch the rear derailleur maintains more consistent chain tension which not only helps with shifting performance and reducing chain drops, it also makes for noticeably less chain slap. With less chain slap comes a much quieter and more enjoyable ride (for me anyway).
Don't get me wrong, if you get into some rough stuff you'll still get some chain slap, but much, much less. The feel of the X.9 shifters and rear derailleur aren't quite as good as the Shimano XT/XTR setup, but other than that the shifting performance is good.
If you want an awesome setup for a much quieter mountain bike ride, I highly recommend the True Precision Stealth Hub, SRAM Type-2 derailleur combination. It has really transformed my riding experience. Through my rides over the last few weeks, I've felt a stronger connection to the trail and to nature and I really think quieting down my bike has been a big part of that.