Love my XD9 SC. Amazing weapon.
I have not shot the .40 out of that platform. When I bought my XD I felt that the .40 would be a little much out of the gun, hence the 9mm. However, seeing how well it shoots the 9mm, I bet the .40 is not bad at all.
I have sensed that people have more trouble with the .40 then the 9, but that may just be me.
The only recurring problem seems to be that some guns have finish and rust issue. I agree that the finish is not top shelf. However, that is always fixable in the aftremarket.
I was going to have my done as soon as I bought it, but I hesitate to change anything on a gun that has thus far proven so reliable. 2000+ rounds, not one burble.