Just to clarify my issue from earlier in this thread, I thought it was only connected to GT6 in the beginning as well, since all of my other discs still worked. As I came to understand, GT6 is a dual layer disc and this issue is related to the laser having more and more difficulty reading dual layer discs and is technically beginning to fail.
Granted, GT6 may be "hard" on PS3 lasers or maybe it's just the age of my PS3, but as time went on, the tilt trick barely worked once every 20-40 tries and many of my other games started failing to read consistently as well, including Rock Band 3 and others. So, I opted for the downloadable, electronic version of GT6 from the Shop, as I received a PSN card as a gift.
The issue is definitely not GT6-specific in my case and I am thoroughly convinced it is the PS3. I may change the laser eventually, as I still have PS3 games that I enjoy playing with my family, but for now, I play GT6 flawlessly with the downloaded version and just tilt the PS3 and repeatedly "push in the disc and hope" when I want to play my other games.
Well, I don't quite play GT6 "flawlessly", as I still appear to have a wall magnet in my bumper every now and then, but you get the picture.