... I think it is a marvel on the VG++ and worse condition LP's that most of us have in our collection. Does knock back a lot of hash and background noise.
IOW, it works by leaving a lubricating residue, which in addition to smoothing over any groove damage necessarily smothers low level detail and dynamics too.
I've heard those effects and I'd never use GG on any properly cleaned LP, which is the only kind I play. Of course I also don't play VG+ records. To me, if a record's worth playing, it's worth finding an undamaged copy. If a record has only mild damage then I'd rather listen through that and hear all of the music. If I'm willing to hear a lower rez version in order to get silent backgrounds, I can play the CD. To each their own of course.