I added these "G Cush" pads to my Grado PS500s today and I really them. They improve the bass and they are much more comfortable. For $45 not a bad upgrade if you have Grado cans and want to try something different. With the G Cush pads, I prefer the iFi Micro XBass off which is different than the standard pads where I like it on.
I did the same a few months ago. I agree they make the headphones way more comfortable. But I'm not entirely convinced yet if the sound change is for the better for me. At least they don't make things worse which is what I was worried about at first. I think I will try them some more again. Especially now that I have the PS1000 I want to see how they compare with the PS500s with the G Cush Pads.
I noticed that the G-Cush required the volume of the source to be increased somewhat to get the same level as the L-Cush pads. I guess it makes sense as the drivers are slightly further from the ear with the larger pads. Certainly more comfortable with the G-Cush
with my RS2's definitely more comfortable. The sound is different, not sure if i like it better than the original pads
With the PS500 I thought it was an interesting change of pace with the G-cush, but ultimately I returned to the stock L-cush. I am sure I'll try them again before long though. It's a nice feature with Grado that the pads can produce a noticable difference and they are so easy to change.