What Chooie said about offset beltloops for IWB holsters is right on target. Loops over the holster get way too thick for me.
RE Lee, I too found the Ctac less than comfortable. Had to carry at 4:00, and then the butt printed when I stooped, or slouched on a stool, which I do alot (not a bar stool, counter stool).
I carry about 10-12 hours a day, and demand complete concealment. I like IWB for my 3" XD and my 4" 1911. I also like a good tuckable for better concealment in more situations. About half the time I don't tuck, and it is fine. Here is a photo (sorry for the soft focus):
It is a Raven Concealment holster I bought here:
The Malabar Front
I found it more comfortable than the C-tac, cost about the same.
I am on holster number 3, all plastic. The other is a Blackhawk Serpa, but it is very not concealable for me, so has become a range holster.
Good luck with your search!