Had a chance to put my EOTech 3x magnifier through its paces today, shooting my agency's qualification course (60 rounds, from 15yds to 100yds, standing, kneeling, prone) and doing some drills. It's on a flip-to-side mount, set immediately in front of the BUIS, as close to the EOTech itself as I can get it.
After zeroing at 50yds, I shot a perfect 300 on the course, and must say that the magnification at 100 and 50 yds really helped. The optics were clear (it was early morning and mostly cloudy, so there wasn't a ton of light available - I could see both the reticle and the targets quite well), the flip mount worked well, and all in all I was very impressed. I shot a confirmation zero at 50 after it was over, to see if flipping the mount off and on changed the zero, and it had not. Most of the drills were at 25yds an in, so I just flipped the magnifier out of the way again and went to work - it was a little strange seeing it sitting out there in my periferal vision, but I got used to it quickly and it didn't interfere with operation or manipulation of the weapon.
I'll have to test it out more (take it on runs with me, in and out of cars, working venues, the day to day duties for me over here) before I make final judgment, but so far I really like it. It is the best of all worlds for a carbine-length rifle meant for engagements from 0 to 300m or so, giving me instant transition from 3x (actually slightly higher than 3) to zero magnification, adding minimal bulk and weight, requiring no change of zero or sight picture, and easily getting out of the way should it break or should the EOTech itself break and I go to my BUIS (I can, in fact, shoot using the BUIS with the magnifier in place, but it magnifies the front sight post and looks a little strange. It won't change the POI very much, though).
At 400 bucks (not including the EOTech itself) it isn't dirt cheap, but I can't think of a better set up that costs any less. At this point, I can't think of a better set up at any price, but that's just me...