USSOCOM issued Safety of Use Message for EOTech sights. The two major problems are,
1)+/- 4 MOA shifts depending on temperature ranging from -40 degrees Fahrenheit to 122 degrees Fahrenheit
L3 Communications, manufaturer of EOTech sights quietly changed their user manual as well as acknowledging potential lawsuit and other fallouts from these problems.
You can read detailed article from Soldier Systems
Coincidently, Battlefield Vegas posted how some red dot sights performed on their many rental guns on AR15.com. It's a good read especially in light of what is going on.
From: Soldier Systems, AR15.com