Well, after about a year with my 229 SAS I started thinking I wanted some nicer feeling grips. It wasn't that the factory ones were bad, on the contrary, they looked great and felt pretty good. But I said the heck with it and bought a set of Nills after reading a couple of posts on several different boards about them.
The end result is a nicer overall feel to the gun. The slight reduction in girth and the subtle contours of the Nills just make it settle in the hand better. The more aggressive checkering gives more control and the look is just as nice if not nicer than the factory grips.
