Handguns are so subjective. Personally, the P239 has always been one of my best shooting Sigs. Strangely, I pull shots left with my P226--P239 puts them right in the bullseye. All day every day. I've had a P228, a P225/P6 and I shoot my P239 better than all of them.
I think a lot of it has to do with hand size/grip size. I have small hands, so I can get a lot of hand around the P239, and a lot of finger on the trigger. Helps me control the shots. I will say I do have Nill grips on mine... which feel just about perfect for me. Though I still shot the gun very well with the stock grips.
Only malf I ever had with a P239 was a FTE with 115gr reman right after putting a brand new recoil spring in. No surprises there. That was also a 1996 model (first year, for the 239 I think). I currently have a 2006 model (SBU serial) which has been flawless.