Finally got to the range to make some noise today.  I do not know how those of you without magazine extensions hold on to this thing!
I shot 50 rounds of Winchester 115 gr Silvertips.  That is WAY more than I will shoot next time.  Feeding, firing, and ejection were flawless.
While certainly not more than I could handle, it was uncomfortable after a short while.  I was very accurate for the first 10-15 rounds, but, I got progressively worse.  I'll have to make sure any encounters with it limit out at 15 shots.  I shot about 100 very lightly loaded 44 special afterward and I couldn't hit anything at my normal rate.
I love the R9S - it is compact, smooth, and like a fine piece of machinery.  However, I will contain my range sessions a lot more than I did this time!
Maybe a little softer grip is in order, or, a glove for range sessions?
I guess I'm formally in the "club" now!