I noticed many people use red dot and holo sights on their ARs while still retaining the front sight post... Doesn't that get in the way?

No, you can adjust the sight dot to be just above the front sight post with the proper mount which will allow you to use the irons if your battery goes dead.

Thats what I thought when I purchased my AR, so I opted for a totally flat-top model and added a flip up front sight and my beloved EOtech. It works great!

I have a Comp M4 on my flat top and have the front A2 post sight. Using the two eyes open method that the Aimpoints were designed with, the front sight is there, but never blocks your view. Also, you can flip up a rear sight and still have a 1/3 co-witness.

you can adjust the sight dot to be just above the front sight post with the proper mount which will allow you to use the irons if your battery goes dead.

 

 

Works great, it's called "co-witness" sights if you've never heard the terminology.