Well, your gun is a Loaded, not a Mil-Spec. Essentially, your gun is a Mil-Spec plus some upgrades. For folks like me, in California, the Loaded and Loaded-Target are the models above the plain Mil-Spec that provide the basic upgrades. Folks outside of California can purchase the Loaded guns OR the Range Officer... The Range Officer is intended to be a better basic package gun than the Mil-Spec, with some upgrades, but fewer than the Loaded.
On Springfield's website, they emphasize certain features of each gun to try to appeal to a slightly different demographic, but in my experience I find that the basic fit and finish (frame-slide-barrel) are the same - And extremely good in all cases. Folks interested in a basic gun will buy the Mil-Spec, those interested in a basic target gun will buy the RO, and those wanting something that looks a little blingy will get the Loaded.
As for extended mag button, well, and grips; Pachmayr wraparound grips offer improved gripping (they do, in fact, make your grip more consistent - They are a great product), move the balance slightly back AND offer protection from certain catastrophic failures (extremely unlikely) that would otherwise result in hand injury. Button and well are to speed magazine changes in combat type competition.
Excluding lemons, all SA guns are capable of very accurate, precise shooting out-of-the-box. That said, they can all benefit from a trigger job, DONE RIGHT, appropriate for the intended use of the gun. I have a crisp 3-pound trigger on one of my 1911's that would be foolish on a carry gun. Most people think the factory trigger on an SA is very good, but it isn't... Unfortunately there are very few folks (and apparently few gunsmiths) who know what a trigger is supposed to feel like. Send your gun to Wilson Combat for a reliability package if you are going to be defending your life with it.
And enjoy shooting your SA!