I have mine and love it! As others have said it is a personal choice. Part depends on what you are wanting it to use the gun for? Is there another gun that can meet that need as well as the Shield?
I have used mine in two IDPA matches, carry it conceal, and shoot it a lot. The Shield was the first M&P gun I owned and since then, I have switched over to the other M&P guns to feel the various roles.
Am I glad I bought mine? Yes. Knowing what I know now, would I wait for to buy me a Shield? Yes. What should you do? Only you can decide that, my friend doesn't want a Shield at all, but is chomping at the bit to get the XDS in 9mm when it hits the market. So it is a very individual choice and only you can decide.