I am jumping on the bandwagon as to great trigger pull. I have never experienced a bad R9 trigger pull in the four I have owned.
I also enjoy stacking. The best acuracy I have enjoyed is when I stack the gun; pull the trigger to the threshold of when it breaks, prior to shot, while focusing on sight alignment.
While I realize stacking is not a very good realtime pursuit with the R9, I still enjoy it occasionally.
With my R9 Stealth (no sights) stacking has less meaning and I pull it until it says Bang.