And upgrade, I did.
Sights.
I started by adding Tru Glo fiberoptic sights. The install was WAY more complicated than I realized. First of all, you have to be sure to remove the sights in the proper direction, as there is only one way the dovetail sight mounts will fit into the slide. Second, those things are REALLY in there. It takes a hell of a whack to remove them. If you don't have a vise to hold the slide, this can be quite challenging. Finally, you'll find the same difficulty in moving the new sights into place. However, if you are like me you might not be comfortable whacking the hell out of your new fiber optic sights.
There are a few tools that can help. I looked into "sight" tools designed specifically for removing/installing sights on my gun. However, they were incredibly expensive for a one time install (approaching $200), and are more suited for gunsmiths who will use them repeatedly. As importantly, I couldn't seem to find any tools in stock. As a result, I ended up just purchasing some reinforced nylon "punches" and beating the sights into place with elbow grease, a large hammer, and patience. I marred the finish on the front sight a bit, which sucks. But I did manage to get them installed.
When I first shot her indoors after that modification, I wasn't sure I was going to keep that setup. But then, I shot outside a few times in IDPA events, and I realized what all the fuss was about. Fiberoptic sights practically glow outdoors, even in overcast conditions. Finding the sight line couldn't be easier.
Trigger.
From there, I looked for ways to improve the trigger feel. As with many standard service pistols, the M&P trigger has a rather long pull, with lots of pre-travel (trigger movement before the firing pin releases), lots of over-travel (trigger movement that continues after the firing pin releases) and a lack of a clearly identifiable reset point (i.e., the point where the firing mechanism resets as the trigger moves back forward after firing). Apex Tactical created a drop in kit to improve these characteristics known as the Duty Carry/Action Enhancement Kit ("DCAEK") which replaced a number of parts. I installed mine with a lot of patience and a few tools, though many might find it to be a bit much and may prefer to take it to a gunsmith.
After installing the DCEAK, the difference was noticeable. The pull lightened to about 4-5 pounds, and the pre-travel and over-travel were reduced significantly. I was pleased. Then Apex upped the ante by creating a new kit that included an entire trigger replacement (the Forward Set Sear and Trigger Kit, or FSST). After learning from the DCAEK install, the FSST install was a snap.
And what a difference the FSST made. Travel issues were eliminated completely and the trigger feels incredible. It's as close to a custom single-action 1911 trigger as you'll find. Well worth the moderate price tag (~$150).
Barrel.
Finally, I ordered a custom match barrel from Storm Lake barrels. This part is the easiest imaginable install -- it's a single part replacement that literally drops in. The hardest part about installing this barrel is waiting the 2 months it takes for Storm Lake to make it once you've ordered it. That said, it's worth the wait. The accuarcy improvements are significant and apparent. What's more, after 250 or so rounds, I still haven't experienced a single mechanical failure on this firearm (which was a concern for me in adding this barrel because the feed ramp that loads the rounds is on the lip of the barrel and differs in design from the original).
In sum, I took a very good weapon and made it great. It's by far my favorite handgun to shoot in my collection. I haven't shot an IDPA event with it since the barrel and FSST install, but I can't wait to do so.
Here's a pic showing the modified trigger and a glimpse of the new stainless Storm Lake barrel:
