I've used a lot of them, and here are my impressions:
Aimpoint QC is hit and miss, we get a lot of M68's that have messed up elevation adjustments, right out of the box brand new. The batteries last [I]forever[I], though. Pretty hard to break them, also.
Eotech, I really like them, but the battery life is a bit shorter than the Aimpoint, and you need to keep that in mind. Pretty tough, as well.
I recently bought a Vortex Strikefire for my personal AR, and I like it a lot. pretty cheap (150 bucks), holds it's zero, and the battery life, while shorter than the Aimpoint, hasn't been a problem yet. Might be about the same as the Eotech in that regard. It is somewhat bigger than the Aimpoint, if that's a concern for you. The only complaint I personally have with it is I wish the dot was a little bit brighter on bright sunny days. Doesn't stop me from reccomending it though.
The trijicon has one serious advantage, NO BATTERIES. I used an ACOG in Iraq, and I didn't baby it, but it held up just fine. Would NOT return to zero if I took it off the weapon, but held zero if I left it alone.
Hope this helps...