Just so you know, the dot on the sight will have to be adjusted to where it is EXTREMELY low inside the sight window for it to co-witness.
The dot will generally be in the center of the glass, unless your looking at your iron sights. Either way, its zeroed. With the Aimpoints, it doesnt matter where the dot is in the glass, thats where the bullet will go. There is really no parallax issue with them. (except up close, at ranges where its really irrelevant) When you look at the iron sights, the dot will come down right onto or slightly below the tip of the front post.
To me, co-witnessing is not a big deal as the batteries on those things last for huge amounts of time and they are extremely durable. I don't know if it is all that necessary to get caught up in the whole co-witnessing craze anyway. It is not necessary but rather just a neat thing to do.
For the most part, I agree on the batteries and mostly using the dot over the iron sights, especially if you dont turn the dot off. If you do turn it off, and you do have cowitnessed sights, you always have a sighting option if the covers are open when you pick the gun up.
If your accustomed to not having the cowitness, you really dont know what your missing. Once you have had a gun that does, you tend to want it available, or at least I do. I've had them both ways, and all my guns no cowitness, AR or AK.
The biggest advantage is, the gun shoulders exactly the same as it does with the iron sights and you get the same cheek weld. You dont have to learn anything new. With the dot, you can shoot with a slightly more heads up posture, but all it takes to get the iron sights is to slightly roll your head down and they're there. The other advantage is, you instantly have confirmation that your dot is still zeroed.
One other nice thing with the Aimpioints that have covers. You can leave the front cover closed and still use the sight. This eliminates the need for the VERY annoying "kill flash" inserts. It allows you to set the dot brightness to a good level for low light, but still lets you see the dot when you go into a bright area, like when moving from shadow to light, or in and out of buildings. It works just like the old OEG type sights, but you do have to shoot with both eyes open and you cant be cross dominant. For a right handed shooter, your right eye sees the dot, the left eye the target, and your brain superimposes them.
