I've got a Burris Fullfield II 3-9x40 on my main rifle, and another on my wife's rifle, both with the ballistic plex reticle, I like them and they seem to work pretty good, I really need to get out on my range and shoot them at longer ranges though to hone the aim a bit. An uncle of mine put a Burris 4.5-14x50 (I think) on a .300 Ultra Mag, and shot it at my range out to 600 yards. And his son used it to take a take a sheep in WY a few years back at a very long range that I'm not going to specify. So I think they work, but some time needs to be spent at the range shooting at different distances to see EXACTLY where it hits at each increment.
Keep the Sun at Your Back and the Wind in Your Face