There is one thing that nobody has mentioned yet so I will.
To go along with that new holster, you definitely need a good gun belt. The normal everyday belt will not do when carrying, especially that M&P 45. You WILL constantly find yourself pulling your pants up on the side you are carrying.
The only way to fix that problem is to buy a good stiff gun belt. I am speaking from experience. When I started carrying IWB. with my Comptac, I was continually tugging at my belt and lifting the holster on the right side to pull my pants up. After I bought a good gun belt from Beltman, all of that stopped.
You will find out what I am talking about after you start carrying for a while without the belt. Just remember, you heard it here