I am writing a review for this sight as part of a school assignment and because it has not let me down since I have purchased it. There is quite a few different sights, however, this one is issued to many different agencies and purchasing a high quality weapon sight was one of my biggest goals due to constructing an AR-15. I love the quality of the sight itself and being able to shoot with both eyes open is a massive advantage due to having more peripheral vision at the range. The 552 doesn't have any noticeable drawbacks from my experience so far, however, it is relatively big and heavy compared to many weapon sights currently available.
I'm very pleased with the unit so far. Easy setup and I like that it has the ability to use my iron sights through the Holo window. No need for a 45 degree set of sights as back up.
There is a lot of debate out there about whether or not the military / law-enforcement version of the EOTech HOLO sight is worth the extra hundred bucks or so. I have multiple of the 552.A65 sights and they put up with a lot of punishment. They're very impact resistant, so you can bang them around a bunch and the reticle stays exactly where you set it. I've never owned one of the civilian models, but out of the 3 mil / LE models I have, they have never slipped. I hear colleagues talk about their civilian models having to be re-zeroed after impact. If you're depending on your sight out in the field, shock / impact resistance is critical. Additionally, it takes AA batteries. There is a lot of debate between AA versus CR-123, but in many countries and rural areas, you might have some trouble finding CR-123 batteries.