I shoot the gun in the stock configuration and do not see any need for changes/upgrades. That constant tinkering seems like a favourite American pastime to me - no offense.
As far as tested loads go, I have shot various factory loads through it (CCI, Fiocchi, S&B, Magtech, Federal, ... 115, 124, 147 grain bullets... FMJ, JHP, etc) and it ran without a single hiccup.
DA is indeed extremely heavy, but SA is incredibly crisp (better than a CZ Shadow 2 I'd say)... almost no takeup, very clear wall, crisp break and extremely short reset. Biggest advantage over the S2: after the reset, the trigger is directly at the wall again, while the S2 has some takeup even after firing a shot and resetting the trigger.