I have the XD Service 45ACP 4". I really can not think of any mods that the gun needs it shoots outstanding I already have the tritium night sights on it. I am a gunsmith and a gun collector so I do all the work on my own guns. I did however paint the polymer part of my XD in Blackhawk Olive Drab. I only use Duracoat firearms finish and what a difference it made. I have been to the range three times since I painted it and I am dead serious everyone was checking it out. I left the mag floor plate black as well as the slide release, slide removal lever, grip safety and the trigger. I was going to paint it Flat Dark Earth because they just came out with that option in 07 but I finished painting a Chinnese SKS in a folding stock with the new SOCOM kit on the front Blackhawk Olive Drab and man did it come out looking sweet. I also painted the reciever and the barrel Matte Black on the SKS.
Back to the XD I don't understand why everyone is intent on having a trigger job done on these pistols they already break clean about 5 to 6 pounds unless you are shooting in tournaments. I can see changing the recoil spring for different or hotter loads especially in 45ACP +P+ its a lot easier to double and triple tap with a heavier spring and keep your rounds on target. I do this all the time with my CZ-52 just by increasing the spring by 2#'s makes a world of difference on loads shooting at 1,800 FPS.