I have a cmore tactical on my AR and love it. It's a great red dot just don't know if it would handle too much abuse, and lack of a sun shade makes it hard to use in bright conditions.
I've got this C-More red dot sight on one of my flat top AR15 SBR's. Works great, and you have a built in BUIS. The bottom picture shows how it sets up on the gun and with the front sight. Not my gun, I usually run a mini-gun in place of the M203.
If you are into competitive shooting with centerfire arms then there is no real substitute for a C-More red dot. The Czech OKO is of similar quality but until recently they were not available in the US for a number of years. Some pro shooters use something they prefer personally (BJ comes to mind because he uses Aimpoint Micros on everything he shoots), but if you go to any match you will see 90% of the open class shooters using C-Mores. Many years ago pros used Optiview or Tasco ProPoint 50mm red dots and you will see some older STI/SVIs with those on them sometimes.
The word NcSTAR should not be mentioned in the same breath as C-More (or Barska, UTG, etc. either as they are no better than NcSTAR). Maybe on a .22 rifle or pistol you can get away with a cheap sight. All my open class pistols have C-Mores, including my open .22 pistol. The only open class firearms I shoot without a C-More are my 2 speed competition S&W AR15-22 rifles. One has a TruGlo red/green reflex sight I have owned for many years and has worked perfectly over that time. I like the green color for high daylight shooting. The other 15-22 has a Pentax HS-20 red dot on it I got off the prize table of the 2012 Ruger Rimfire World Championship. Both of those red dots have more than sufficient brightness for high noon summer matches which can't be said for most of the cheap red dots out there.