The M&P line has been around for a few years. They have a strong following with armed professionals & the shooting sports industry.
For specific questions about the S&W Shield pistols, I'd review or maybe contact top pistolsmith & SWAT unit commander; David Bowie of www.BowieTacticalConcepts.com
. Bowie is widely known for M&Ps & Glocks.
For sights, Id look at the Trijicon HD line or maybe the XS tritium.
The Shield is new but after market parts & services will soon follow.