I tested a G17 with an RMR for a while a few years ago. It definitely made the edge-case shots (SOTM, low-light, pouring rain, etc.) easier. It was slower for the up-close stuff, and while I didn't do the work it would have taken to master that stuff, I felt that it would have been possible to run very nearly as fast as with irons had I been willing to put forth the effort.
Right now, I'm waiting for the technology to improve and for prices to drop.
Okie John