I got my .40 Shield on Friday and got to shoot it a little over the weekend. It shoots well and is a great price for what you get.
I think my XD is made a little better. The take down lever and slide release are machined pieces on the XD, the Shield has stamped out and formed pieces for the saftey and slide release. I prefer the safteys, chamber indicator, striker idicator and ambidextrous mag release that the XD has. I don't understand the trigger saftey on the M&P and it bothers me some that they made the trigger itself out of plastic. The recoil spring was very rough to begin with on the Shield, after some shooting and a bath in engine assembly lube it was ok. I don't know what is going on with the slide release on my Shield but I can barely operate it with one thumb, super stiff, and maybe my main complaint.
The trigger on my XD is a little mushy but not bad. The Shield trigger is very heavy and crisp. I prefer the XD.
Just my opinion. I chose a Sig P250sc over a 3" XD for a subcompact double stack. I got this Shield because I wanted a .40 single stack and got sick of waiting for Springfield to come out with the XDs 40. I wouldnt trade this Shield for a XDs 9mm but I would trade it for a XDs 40.