If the mag release is broken in some way, I have heard of Glock replacing the ambi frame with a standard mag release frame. I don't think that they will replace it due to you not liking it.
My 21SF has the ambi release and I did have a few problems with it sticking at first , but I did some sanding on a few spots and now it works great. I have about 4000 rounds through my 21SF and the mag release isn't as stiff as it was when I first got it , so it may smooth out with use.
Most of the stuff you speak of in your examples can be overcame with training, but if you are unhappy with it , you can always sell it and buy an SF with the standard mag release on it.
I was unhappy with mine at first , but the more I shot it and worked with it , I got use to it and it got use to me.
I normally agree with "use what works", but I think Glock was trying to answer the call of people wanting the ambi mag release, so they introduced it on one model. While not a complete failure, I don't think I would classify it as a complete success.
The Gen4s are IMO Glock's attempt to catch up with the competition. The backstrap design was a half-a**ed attempt (IMO) as well. They should have made it a slide in ordeal where you can have a Flat profile, SF profile, or a full glock profile backstrap, but that's just me.
I own a Gen4 G17 and It has been an excellent firearm so far. I like the larger mag release, slightly reduced grip, reduced recoil, and the new grip texture. Only time will tell if it will be a success.