As you can see in the photo above (you can click it to view a larger version), this gun has some purple stripes, and an area just forward of the barrel that's also purple. This is most likely caused by uneven heat treatment of the steel. It doesn't seem to hurt the gun, and any detraction is apparently purely cosmetic.
In this photo you can also see the screw that mounts the rear sight to the slide, as discussed on the previous page. The screw that's to the right of and below that one is for mounting the extractor spring, which is simply a piece of spring steel.
I have read a few complaints about the PF-9's recoil, and I have to say that I don't agree with them. A couple online "reviews" seem to feed off each other, with both likening the PF-9's recoil to the kick of a mule. I fail to see the reason for these and similar comments, as the gun didn't seem to kick much for me, and I fired a variety of ammo in it. I also saw complaints about "trigger slap," but again, I had no trouble with that. This pistol is plenty comfortable for me to shoot.
Speaking of comfort while shooting, I have read that some of these pistols are plagued by excessively sharp edges on the raised, mostly-rectangular, shapes on the grip. Fortunately, my pistol doesn't have that problem, and offers just the right amount of texture.