I posted on this forum last week about a tasco Propoint (looks like Aimpoint). it held zero in sub freezing temps during 200 rounds on my scout squad rifle. the dot is the clearest I have seen for around $100 optics as well.
I like it. Will run it until it dies, then I'll go Aimpoint
I ended up buying a Walther red-dot that had good write ips around the web.or now. I could not justify expensive optics at this point considering the fact that I have never even shot an AR15, and I want to make sure its something I enjoy before dropping 3-400 on optics.
If the AR platform is something I end up enjoying (which I think it is) I will invest in an aimpoint, but until then the walther will do.
I also plan on getting some reasonably priced iron sights as a backup system.