And the striker pins and springs a good deal to do?
If you are asking if it is difficult to do, if you have (and know how to use) a roll pin punch, it is not too hard. If you are asking if it is a good idea, some of the trigger kits will come with the lighter striker spring. This will require you to remove the striker retainer pin, so you might as well replace it with a more sturdy roll pin if you are doing the trigger job.
What does all the upgrades for the striker system do?
The stock striker retainer pin (roll pin) will likely break at some point. Others have told me the striker retainer pin won't break if you are using snap caps or the like to absorb the striker energy; however, I ALWAYS used snap caps and my pin broke around 3K rounds. Some companies like Powder River (and Springer Precision?) have upgraded replacement roll pins. I ordered a bag of roll pins from a screw/bolt/fastener/etc retailer online. Got 25 of them for something like $7 + shipping. So far I have only used one and 6K rounds later it still appears to be in great shape.
If I remember correctly, the Powder River Precision (PRP) trigger kit comes with a lighter striker spring to help lighten the trigger pull. I installed the PRP Ultimate Match Trigger and it has been GREAT! I didn't get the pull down to the 2.7# that GJSchulze ended up with. Mine is about 4.5#.
If you install the PRP trigger with the over-travel nub, and you may be shooting in freezing temperatures, you will want to make sure that you sand enough off the nub so that it still fires with AT LEAST a business card between the nub and the back of the trigger guard. Personally, I placed two business cards between the nub and backstop to make sure it would still fire. When the plastic trigger drops to near freezing, it expands and could intermittently not allow the gun to fire no matter how hard you mash the trigger to its full travel...Ask me how I know.
Regarding the legality of the Ultimate Match Trigger in USPSA, it IS legal in all divisions. Specifically, it is legal in USPSA Production Division because it is offered directly from Springfield Armory. However, the upgrades you are talking about (ported barrel, red dot, etc.) will not allow you to shoot in USPSA Production Division. So the trigger is a moot point.
A red dot will put you in the Open Division of USPSA. If that IS the route you are going, then you have a LOT more money to spend. For example, an open holster, mag pouches, and a magwell funnel will be a MUST. However, when you are all done, you will still have a 4.5" barrel XD and will be competing against shooters with ported 5" custom fit barrels shooting a hot 38 Super Comp load. That's stiff competition.
Regarding the PRP polished striker. I believe the benefit is a striker that moves more freely providing consistent firm primer strikes since there is less friction impeding the striker movement.
Fly