I handled one the other day. I was surprised by how much plastic was on it.
Frame was plastic, with some steel inserts on stress areas.
The slide was metal..... with plastic on it.
The magazine was completely plastic.
It made for a nice, light package.
I liked the idea of the safety being above the trigger guard, however I think my fingers are a little long for it because it felt a little akward to bend it to engage/disengage, and I think this could pose a serious problem for officers with smaller hands. The magazine well was longer than the other handguns I've handled and felt a little weird at first.
The ballistics of the 5.7 don't justify the cost of the switch, and flat-out are pretty bad unless your goal is to puncture armor and do nothing else.
ETA: now having said that, I'd like to get one before they're banned.