I bought an x-bolt composite stalker in 300WSM about 2 years ago. It shot 1" groups out of the box. I've been slowly working up a good load on it so really can't say if I've dialed in its best accuracy yet. But I'm still shooting about 1" groups at 100 with Nosler BTs, and my first tests with only a few shots downrange at about 450 yards were pretty much where I expected them to be - about 5" groups. It is very likely that the gun shoots better than me right now as I don't have a lot of time behind it yet and am still getting better myself. So for accuracy, I don't have any complaints, but this year I have expectations to get it (and me) to shoot considerably tighter. We'll see...
The overall fit, feel and balance I find perfect. The composite stock is nice and light, has a great feel to it even in the wet and cold. The trigger is very nice and for my purposes breaks very cleanly, crisply and consistently. A more experienced shooter might have a very different perception though - I'm not going to be the best judge here. The x-bolt scope mounting pattern is a neat idea. No doubt the bases lock on there very tight and secure. That being said, there are relatively few bases you can get for them.
The downside...
The action doesn't seem to be the smoothest and most precise action in the world. The bolt seems to have a good deal of "slop" until it is locked in. Not sure if it will ultimately limit accuracy that way but is not what I would call a precision built action.
I found that when it started getting hot, the barrel would start getting tight to the stock. Found a few high spots in the stock that I was able to cut down to better float it.
And like sp6x6 said, there just isn't much "aftermarket" for it. Maybe you don't need it. As far as I can tell so far the barrel is just fine. But if you wanted to rebarrel, drop in a new action or trigger, there aren't a lot of choices out there... if any.
Overall I am very pleased with it. I find it a very capable rifle that even in my current state of practice with it am already at least "good enough" out to about 500 yards with high hopes of stretching it to 700... at least for target shooting at first. For a whitetail hunting rifle with the possibility of one day doing some big game hunting, I have no doubts it will always suit me just fine. Whether or not I can get it to print targets like yote doctor showed above this year will determine if it really settles with me. Of course... without spending a lot more money, it would be hard to guarantee much better than that anyway.