Get the Shield
I am one of those who initiated a thread about the problems I had with my Shield's RSA. It came from the factory with a bent rear RSA spring retainer disc. At the time, I did not know what effect it might have on its performance. Now with 1000 rounds through it, I know the answer: very little. The Shield has performed very well, though not perfectly, since I bought it. My only concern is that it has an FTE rate of about 1%, which I regard as higher than desirable for a self-defense weapon. (In contrast, my M&P 40c has an FTE rate of 0% through 3000 rounds. S&W set the expectation bar pretty high with the 40c.) Overall, though, I think my Shield is a fine, fun-to-shoot gun with an excellent trigger and a surprising degree of accuracy for such a short barrel. And its FTE rate may be ammo-related – I'm still experimenting with different brands and weights.
I have continued to contribute to my original thread because my problems are not with the Shield as much as they are with my attempts to get an undamaged RSA. It has now been about 2½ months and I still have no functional replacement. Things have been so strange, I am beginning to find it amusing. It's kind of an adventure now, wondering what S&W will send me next. (I would not be so amused if my Shield was out of action.) Nonetheless, I have posted many positive things about my Shield in various threads. For an example, check out my post under "Rastoff's Challenge II" in the Concealed Carry section of General Topics.
All of the above has been a long prolog to my main point: You should get the Shield.
It is a great gun, and you can ensure that it will be so from Day 1, if you give the RSA a thorough inspection before you buy. Here's what you should do:
(Do not deal with any seller who won't let you do this.)
First, lock back the slide, and gently pull and twist the disc on the front of the RSA's protruding inner guide rod. It should be tightly attached to the rod. If there is any movement of the disc at all, the RSA is defective and will come apart in the near future. Move on to another Shield.
If the front disc passes the test, have your friendly salesperson remove the slide and the RSA. Examine the RSA's rear retainer disc. If there is no sign of bending, you're good to go. If it is bent, you can do one of two things: look at another Shield, or; if it isn't bent too badly and you're willing to take a risk that it won't hurt the Shield's performance, use it as a negotiating tool to drive down the price.
Finally, once you get your Shield, make sure that the RSA is fully inserted, straight and level, whenever you reassemble it. Then your only problem will be with your ammo budget, because you'll find yourself shooting a lot of it through your new Shield.