I do not have any info on the MRAD and do not intend to thread jack. If you have poked around the Barrett forum there seem to be a hand full of people willing to pay the price for a MRAD or M107A1 but seems more and more people (current Barret owners) feel Barrett has become FAR to proud of their equipment. Just give it time the market will adjust it's self.
I fired a Barrett MRAD last January. It was a .338 Lapua. I believe that will be the initial caliber and the other calibers and barrels will not be available for a while. I think the best price I heard was around $5400.
For shooting, it was a nice rifle. I only got to shoot a couple of rounds. Both easily hit an 18"x18" target at 600 yards in 20mph winds, and I am not the greatest shot. It was supressed however.
So, I am looking at getting a long range rifle next year-ish. I was considering this because of the versatility, but @$%^ the price is a killer. The issues for me are;
1. I already have a 308 and can reload these so that is handy. But out of the 3 this is my least preferred caliber for my new project.
2. I already have a 300 WM so at least I wouldn't be adding an additional caliber if I went with this.
3. 338 Lapua? arguable the best, but would also be the least "convenient" for me.
With the MRAD, I could "plink with 308" and then shoot the other stuff when I chose.
Before this came out, I was planning on getting a remi 700 in 300 WM and working on it over time to minimize upfront cost.