All I know is from the folks that I have spoken with over the years who rely on their optics in real world situations, mostly contractors and a few active snipers. The one thing that came out as a true-ism is that you should expect to pay about 2x what you paid for the rifle for glass. These guys are shooting $1500-4500 rifles and forking out $2500 or more for high end S&B optics or the likes. There are several mid range manufacturers.. Leupold, IOR and Night Force come to mind.

The point is, that the more you pay the better the optic will be, and it is very noticable. Going from my little Elite 3200 to the NightForce was like night and day. Much sharper imaging and finer adjustments. This isn't to say that for the more casual shooters that the Bushnell, Burris and lower end Leupold and Nikon optics aren't going to fit the bill. But just remember, Pay Once, Cry Once.