I have an XD 40 Tactical and couldn't be more happy with a handgun.
For everything you ever will need for it check out this guy.
http://www.pistolgear.com/
Also go to the pistolsmithing link on that site and check out Canyon Creek, Rich does an awesome trigger job on the XDs, I have not had mine done yet, but it will soon be done.
For everything you could imagine being talked about for the XD check out this forum board.
http://www.hs2000talk.com/index.php
I have the Stainless steel guide rod in my XD and the 22lb spring, made one heckuva difference in recoil/alot faster to get back on target as well. Also put a set of Trijicons on my XD and love them as well.