I really like the Millet DMS 1x4, good all around scope, true 1X so with the reticle illuminated its pretty much a red dot and you can keep both eyes open, with the zoom at 4X you should be hitting good out to 300m easy. I think its very good for the price (~$220) but its a big honking thing -- my only real complaint with it.
But my favorite inexpensive red dot for the AR is the Barska M16 Electrosight, about $70. Add a cheap UTG flip up rear (~$30) and you are not out of action when the batteries go dead. I've been very happy with the battery life, but if you leave it on when you put it up, it'll be dead next time. I've even been very happy with it on my LAR-308 while waiting for its back ordered EOTech to arrive.
The Vortex Strikefire is a nice step up at about $150 and will give a true co-witness with the irons, whereas the Barska Electrosight you are using the bottom 1/3 of the optic with the irons, but its parallax-free enough that this still works very well for the initial mounting and shooting with the dot on looknig through the rear aperture. The included 2X magnifier is crap -- looked through it once and threw it away, but its a nice red/green dot setup, I almost always use mine on green.
IMHO if you want something cheap to use while you research and save up for better the Barska M16 Electosight is the way to go. But be aware, most other Barska red dots are crap.
--wally.