Either I am way late to the party and never thought about this, but while doing a lot of drills and having 5k rounds through my M9A3 already since December, I picked up a little trick. With my grip while firing the pistol, my strong hand (right handed) has the tip of middle finger just above the magazine release button.

Instead of raising the pistol up and at an angle in my workspace, dropping the mag via my thumb, reloading and then reacquiring a correct grip, on the M9A3 I can easily drop the mag with my strong hand middle finger, reload while having my grip unmoved and then go right back to it. On something like the FAST drill, it shaves a second off my time on average.

Anyone else do this? Is this common and I just never saw it?

BTW have never been a Beretta guy prior to the M9A3 and absolutely love it. It's taken over as my favorite go-to handgun and loves shooting the Winchester NATO spec 124g ammunition.

I don't do that. Just tried and while it does work, it's a lot more difficult for me to do than simply doing a thumb press. I have larger hands though so it's easier for me to just use my thumb. If I want a bit better purchase on it I just give it a quick wrist flick to just it a little further back and then flip it right back as part of my reload motion. Been shooting the M9 for 12 years though so there's a lot of stuff I do with it that's kind of unconscious till I actually think about it.

Also perfected a cowboy-style back-into-the-holster twirl, although I don't do that at public ranges so people don't shit themselves.

Us lefties have been doing that for years, with all the right handed pistolas.  I cannot imagine using a thumb on a mag release.  (except I don't use my middle finger, I use my pointer)  The middle finger would be weak and awkward to me.

OK, I can be a little slow and dense sometimes.  How is your strong hand middle finger ABOVE the mag release?  It would have to be a huge curve up from the bottom of the trigger guard.  

My middle finger sits right below it and I don't have enough length to move it up and hit the button.  I might have shorter fingers but I don't see how you'd do it without breaking your grip.  

You got pics?

Apparently I'm dyslexic lol It's below it as well.

Your hold and finger length/hand size I'm guessing has to be within a specific range in order to pull this off. Too short and you're needing to change your grip to get at the release, too long and youd need to do some weird finger manuever to come back over it. So neither of those would work.

Instinctively I still go for the release with my thumb; was just curious if any right handers ever used this to their advantage.

I know a couple that swapped it over to the other side and use the strong hand index finger.  Never heard of anyone doing it the way you describe. If it works for you, great!