Lots of people are now carrying the Trijicon RMR daily on their sidearms, and many swear by it. So long as you have good backup iron sights and it's concealing for you, I'd have no worries about it. We've had several folks go through the school with them, and do well. I think you would definitely want to put LOTS of rounds through a gun so equipped to accustom yourself to "the eye finding the dot." Should be particularly worthwhile to try for anyone who's having trouble seeing iron sights at speed.