I have looked at that accessory for months now, and I like the idea of something covering the inside of the top of the trunk lid. I have not seen the pictured GM version in person, but it looks like it is gray or charcoal--about the color of the hood liner. My car has Brownstone carpets and I put a Brownstone Lloyds Mats (silver StingRay logo with silver Stingray emblem) on the trunk bottom. It is excellent quality, plush and fits perfectly. I looked at Lloyds Mats online and they did not offer a trunk lid liner. So, I emailed them to see if they had one or would make one for me. That was a couple of weeks a ago and they have not responded. I will probably try to reach out to them again. I was very impressed with the quality of the trunk mat. Actually, it was nicer than the "premium" mats that came with the 3LT. BTW, I got the trunk mat from RPI (a forum supporting vendor), as I recall.
Installed it after got car home. Very easy install, but you must drill holes and be careful not to drill through the trunk hood. Rather simple install, I used some two sided tape to assure the alignment was even before I drilled the holes. Love the look and the addition.
I refuse to answer that question on the grounds... Sure, the "soundproofing" would be minimal. But, the cosmetics are what it's all about. It makes the underside of the trunk look more "finished" IMHO.
Anyone know why the trunk lid liner has been discontinued? I order the GM OEM one and it did not fit. I sent it back order another one from my dealership and they said it was no longer available. Very odd.....