G'day all,
I just found this thread on red dots and thought I would add my experience with them. I have used them on both a .303 smle sporter and a .458wm. and intend using one on an o/u DR. They both were cheap Chinese versions, but both worked extremely well. The fact of fast target acquisition with both eyes open as has already been stated is very real. Another very usefull point is that the dot is sized by moa, so is always a known factor at any given range. eg: 4moa dot being 4" at 100yds but 8" at 200yds
gives you an accurate gauge for holdover. The one on my .458wm Ruger #1 Tropical Rifle handled the recoil with with no loss of accuracy (max loads), but was totalled by a friend dropping some gear on it while away on a hunting trip. So care is needed with the light alloy construction.

All the best, Ian.