Well I have not decided, I did buy two APEX kits for my two M&P40C's (4.0" and 3.6") but have yet to install them. I am waiting to actually shoot the guns to confirm function and no need for warranty work prior to installing them. I bought the kits even though I was happy enough with dryfiring the stock triggers. A truck forum had some glowing recommendations (Funny they were from Arizona... Just kidding, anyway I have them.) Eventually they will be in them.
Meanwhile I have a Shield 40 (1.0) and am wondering is it would be reasonable to upgrade the trigger on that. The APEX kit lists for it at $165. I have shot this gun and it's companion 45 and was happy enough with both. Regarding the 40 specifically it seems like a lot to invest in a $300 gun that I carry little. Is there a 'night and day' difference?