Ok, here is a photo of my JCP40 on the left with the rubber spray on the grips and my NIB C-9 with stock grips. Hard to "see" the difference except the rubber is somewhat duller or flat looking. The C-9 still shows some of the OEM plastic texture, while the spray rubber fills in this texture and provides a no-slip grip overall. May not look that much different, but in your hand you can really feel it.
If you do this, remove the grips and balance them on a post of some sort, like small medicine bottle, or tube or whatever doesn't stick out beyond the grips edges. First clean with alcohol, let dry completely then with clean fingers (no skin oil) place each grip on the tube, post, whatever, then following can directions, spray a light but COMPLETE coat on all surfaces and edges but not dripping or puddling, so it looks very shiny overall, and let dry at least 30 minutes. Then repeat the procedure 3 more times for a total of 4 coats. Let sit 24 hours before handling and remounting on gun. Piece of cake..... I have no idea about durability as my 40 has had the rubber for about 3 months. BUT, it is my bedside gun so it gets almost no handling at all. Now, I also used the rubber on my carry gun, my CF380 and I have noticed absolutely no wear or abrasions, so I think it is tough stuff. Nice thing though, is that you can remove the rubber by peeling off with a little solvent. At Lowe's - Performix Plasti-Dip, about 7 bucks, enough for 4 guns. Good Luck