I have one in 6" sst GP-100. It was heavy hammer and trigger when I got it new. After the first 50 rounds of ammo through it, I took it to may favorite gun smith and he did a trigger job and hammer spring. It is so sweet that if you close your eyes and dry fire it double action it feels like if you are shooting a Python revolver. In single action is great and it breaks the trigger at the same feel as the S&W 686.
The revolver (bought in the 1990's) is capable of tight groups to many different loads of different bullets, primers, and powders. This revolver is definitely strong!
Now, I am not sure about the latest batch of GP-100's I have read in this or in another forum that Ruger GP-100's are not as good as they used to make (accuracy wise I guess). But I have not bought one lately so someone else that has would have newer information on them. My GP-100 has the grip that is rubber with a wood side plate. See attached picture. (I tried to attach pic but it did not work)
Good luck with your purchase.
Camba