I have the Shield PC w/ FO and love it. 400+ rounds so far and its been perfect. I've been able to use the sights in a darker indoor range ok (and if it comes up in discussion due to the PC's porting, any muzzle flash has not been a problem for me either).
Can't compare it to a regular Shield, though I let a range officer try it (he carries a Shield at times) and he thought the trigger was nicer than his stock version and the muzzle flip was less as well for a quicker follow up shot. He too didnt notice any flash while watching me shoot it, that would concern him anyhow.
If it means anything, my wife on occasion hits the range with me and has shot my compact and full size MP's fine for one who rarely shoots. But she prefers to plink with the .22's instead. The first time she tried the PC Shield? After the mag went empty she asked if she could shoot it again. So for her, that said something.
Back on track, I personally like the FO sights but that's just me. Never had a gun with night sights, a laser, etc....
If i am ever in a situation that is so dark the sights aren't of any help, I either would be point shooting or if the target is hard to see as well, likely wouldn't be firing in the first place. Just my .02 of course as there are many variables in that conversation.