I installed a Springer Precision trigger kit on my XD9SC. After the first time taking it apart and putting it back together, its pretty easy. Installation was a snap, just took a bit of sanding/fitting to fine tune it to your gun (there is extra material that you have to take off). I also polished the Springer sear even further, as well as the striker mating surface. Resulted in a super smooth trigger.
I was happy with it, and plan to buy one and install it in my XDmC.