I've been thinking about upgrading my wife's carry pistol. It's nice to know the Shield performed well, that one is on the short list. I really wanted the Remington R51 to be a contender, but it has been receiving very poor reviews.
The R51 is a nonstarter IMHO.
The Sheild was an impressive little gun. Again, I had zero malfs and she had two or three stove pipes. My wife is 5'4" x 115 pounds with very little upper body strength. The gun was stiff when new, and needed a strong wrist to keep the poly frame flex from short-stroking ejection. After I identified why it was SP'g we modified her stance and it cleared up. I think it'll be 100% for her (even if limp wristed) when it is fully broken in.
I forgot to add originally, it is nearly impossible to seat a fully loaded 7rd mag. You have to conduct the ill-advised "pop the base plate" to get it to seat / mag catch to engage.
Not a big deal, but worth noting.