I know a growing number of firearms instructors who have either bought or have ordered Shield 9's (after trying one). These instructors represent a broad range of experience, and include folks who are dedicated 1911, Glock & TDA users (TDA is Traditional Double Action, or DA/SA as it's sometimes called) users.
Of course, they've also been buying and using M&P's, too.
I spent an afternoon working with a Shield 9 (belonging to another instructor). Even though I already own a fair collection of smallish 9's (a couple of G26's, SW999c, CS9 & 3913), I'll be ordering a Shield 9 of my own in the near future. I have little doubt it'll replace the slightly larger & thicker 9's I've been using for many years, and might result in my 5-shot J-frames seeing a bit less retirement CCW use, as well.
Being an owner/armorer for the M&P pistol series, I don't mind the sear disconnect lever and field-stripping method for the M&P series. Hey, I got used to reaching into the open ejection port of the Ruger P-series pistols many years ago. Not hard to do, and it definitely gives the owner/user an added opportunity to make sure the weapon is EMPTY.
I found the Shield 9 to be reliable, with nice ergonomics and a slim profile (overall), excellent controllability and surprisingly good practical accuracy.
I generally don't over-concern myself with service/duty "triggers", but the trigger on the new Shield 9 I used for that afternoon was quite nice when compared to my G26's & 3rd gen S&W's. Only my compact 99-series (SW999c) has a "better" trigger.
I don't make it a practice to "recommend" handguns to folks, preferring to work with them on a practice/training range so I can get a good idea of their experience & skillset.
Trying to find one that can be tried (rental?) before deciding would seem a prudent idea.