Just wanted to share my experience here.
I mostly lurk here, owned many B Body cars but have been driving Ford panther platforms for the past decade.
Switched jobs recently and got a 2015 Impala LS Limited. One thing that was lacking was the non HMI stereo. Was looking for an aftermarket solution and then stumbled upon jtrosky's post.
Communicated with jtrosky many times, he was patient and answered all my questions, and low and behold, here we are, an 8th Gen Impala with aftermarket XM Radio that works seamlessly with the GM1010.
I bought the kit from jtrosky for the GM1010, bought an aftermarket backup camera that mounts behind the license plate (just the camera head sticks out), a junkyard impala roof antenna from LKQ with Onstar and XM (my antenna only had the Onstar cable), an antenna cable to go from the roof antenna to the SXV200, an isimple GM XM Radio kit, and an SXV200 XM tuner.
Installation is just as simple as everyone else says. I had it one in less than 3 hours, the most annoying parts were removing the back seat to do the wiring for the camera to the head unit and pulling down on the headliner to get the roof antenna swapped out. Everything, including the XM radio, was all plug and play.
I did have one issue, and that was the XM radio not being recognized by the head unit, which was due to the fact that I didn't read the directions for the isimple, which states you MUST plug in the SXV200 before you plug it into the cars harness.
Other than that, it works flawlessly. A great solution for those that want to get XM and have a factory look in their head unit.