They work and can work extremely well, but they take time to work out the yardages (the cross-hatches will not be exactly dead-on at say 200, 250, 300 etc)
I used the Boone&Crockett reticle to take a deer a couple years back at 326 yards.
A better way to go is an M1 dial or turrets. Much easier to figure out and your range is only limited by the amount of elevation travel in your scope (likely quite further than necessary).
I may be getting rid of several Leupold VX-III B&C scopes. Either changing them to duplex and dials or buying new - if I can get 75-80% of my money out of them. PM me if your interested in one.