stcyr, I've been using the Sub-9 (set up for G-18 mags) for about two years now.
I haven't kept any accurate count of how many rounds have been through it, but it's a few cases (probably between 3 & 4 thousand rounds).
I went through one box (1K) of the SA stuff right after I got it. The bolt wasn't going all the way back for the first mag or two, but it loosened up by the third mag, & it's run 100% ever since. The 2nd, and 3rd cases through it were the HOT Hirtenberger buzz-gun ammo.
The only reason I used the subgun stuff was because I found nine cases for 8.5¢ a pop. This could be my imagination, but I don't think so - THAT'S the ammo that mine likes best! I don't think it's EVER had a FTF/F/E with the hot stuff.
I don't know anything about the Sub-2000 (I haven't even seen one yet), but I don't know why they'd want to change anything at all on the Sub-9.