I've had a 9mm M&P Shield for over a month and purchased a M&P 9mm FS recently. To me the triggers feel about the same, both are smooth (no grit) and have crisp break.
Bought my M&P Shield 9mm 2 1/2 weeks ago at Academy sports after search for several weeks. Applied for my CCW the same day and received it in the mail yesterday (7/7/2012). Life is good.