I am suppose to look at this scope tomorrow, for $800.    Is that price fair ?  

It will most likely end up on my S&W M&P10 308 rifle, which I use for deer hunting.

 also, it has the retical that is a triangle, which brings my next question -  how will it do at the range when shooting for bulls eyes ?  As a reloader, I like to shoot 1/2" groups, Im just wondering how precise this is for such shooting.

I looked at a similar trijicon at the store for $1250ish + tax and it had an actual cross hairs which seemed REALLY nice...  im wondering if I will hate this style retical

https://www.trijicon.com/na_en/products/product3.php?pid=TA11E

ACOGs in general are not precision optics. They have VERY good glass, and are extremely durable,  but are designed as a combat optic, for shooting humans under adverse combat conditions.

If you are looking for a precision optic to shoot small groups at several hundred yards, you are making a poor choice.
If you want a bulletproof optic for fast shooting, then an ACOG is an excellent choice.

$800 isn't a bad price for a used TA11.

Bullet proof optic for fast shooting, well that should work good for deer hunting.  

I could take my current Leopold 3.5-10 x40 scope off of this 308 to put onto a different rifle.

I'd think you'd have a difficult time shooting .5 MOA at 100 yards with that ACOG. I'd stick with a traditional scope for killing deer, the ACOG is very specifically built with killing people in mind between the BAC and BDC reticles.

I guess the reason I want this so bad for deer hunting is that at times with my vision the cross hairs in my vx-III Leopold sometimes disappear when trying to focus on them. I dont want to miss a nice deer over something like that and I usually only have it on the lowest 3.5 power setting. But I'm taking these comments into consideration and maybe its not the right choice.

IMO, they are the best combat optic for 50-400 yards. They are excellent for hunting. Killed a deer using one last year.

They are not the greatest for shooting paper groups.

Check out Trijicon's Accupoint line.

It's also very good for killing deer, for all the reasons it's good at killing people.