I hope you asked because you would rather spend $400 to $500 on a good used all metal classic than spend it on plastic.
I'd give the Shield a + on it's ergonomics but nothing more. Don't forget the 3913 series, in particular, the early 3913TSW with the short grips.
While I love the 3rd generation guns and prefer to carry one for my own defense, I don't hate the shield. My daughter is small, at 5'0" and left handed. While she shoots my 3913 NL pretty well, she hates that it only has a left side decocker/safety. She's held my 3913 and shot my 6906, but I think either would be too big if she ever decides to get her concealed carry license and carry for her own defense. She shot my M&P9c when I had it and it shot well. What she hated was loading the magazines, but I think that was a function of a couple of factors which she can overcome.
Which is my long winded way of saying that at some point I'll be looking at buying a Shield in 9mm to try out. I can do that knowing that if she decides she doesn't like it I'll very likely be able to make my money back when I sell it.
Of course if I could find a CS9 at a reasonable price, having it converted to DAO would be an option. I have one, but much as I love her, I'm not going to give that one to her!