I've like my BDC reticle a lot. My Nikon 3x32 P223 on my AR has it. Definitely worth the investment if you want to hit some longer range shots that you don't go to the range and zero at.
Its a pretty simple setup process. Just zero your rifle at a know distance. Then go on to the SpotOn web app and enter in all your shooting information: scope, bullet, distance, etc.
I've written an article that explains the BDC in depth and goes into why it is a good buy: Why You Need the Nikon BDC Reticle