Joe,
Your image compositions and processing are stellar, and your eye for capturing expressions is excellent.
That out of the way, understand this comment is not about you or your images, it is about the performance of the lens only -- I hope you don't mind because the lens is new, expensive and as such draws a lot of attention: I see what appears to me as just plain soft -- images missing that sharp-edged glint, seen especially lacking on the speculars in the child's eyes. It almost appears as bad to my eyes as slight subject motion blur, or simply a poor lens. I'm sorry, just sharing what I see and it's not just your lens either. Jan posted an excellent composition and low light capture of a firetruck in the dedicated 58G thread, and I see the same lack of crisp detail -- and he was shooting at f2!
Sorry folks, I just don't see anything that turns my crank from this lens yet. In fact the only good thing I can say about it is I like the way it renders oof background highlights, and that's about it.
Sorry,