I put an XS Big Dot express sight on my Kahr MK40 about a year ago (http://www.xssights.com/store/catalog.pdf). At first I found it difficult to use, but I have put a couple thousand rounds thru and I now like it a lot. I find that I can get on target faster with it than with any other sight. The trade off is that I lose a bit on accuracy for slow fire. I don't think that this is big problem though, as my primary goal is 5-6 inch groups with the greatest speed possible. That usually means (depending on the distance) a flash sight picture or Applegate-style point shooting where one brings the gun up into the line of sight but doesn't get a real sight picture. In either case the Big Dot really sticks out. Does anyone else have experience with express sights, either for big game rifles or for handguns? Does anyone use them on an M&P? I have not yet put them on my M&P 40 but am thinking about it.