The SPR grip is pretty good, the plastic can get pretty slick if it's hot out so I stippled mine for better texturing over the grip tape I was using before. I still need to modify it for an ambi-safety and then I'll probably throw it back on my 18" SPR.
One quick note, my SPR grip came with a safety detent spring hole that was drilled just a shade too deep, although I'm not sure if mine was a fluke or that's just how they do things. It still allowed the safety to function but it wasn't as positive as I'd have liked so I clipped a small section off an extra Glock trigger housing pin and dropped it into the hole. The diameter was a perfect slip fit and the safety detent is strong and positive. Just something to keep in mind.