Plenty of people use them for the P Series polymer framed guns and the SR9 as well. People will use the Handall Jr. for the LCP too. Heard good things about them, but like the grip of the SR9 as is so I have no use for one.
I have the regular attachable grip (not the slip on) for my KP944 and love it. I dont think I'll be doing anything with the sr9c since it will be a carry gun and dont want to increase the bulk any. The sr9c grip is comfortable but I do find it gets a bit harder to hold onto if my hands are sweating.
I have the hogue on my p97 which fits great. On my p95 I like the pachmayr slip on better. The p95 grip is thicker than the p97 and the hogue has palm swells and the pachmayr doesn't. Both will help with gripping the gun. Mark