The Classic Army Elcan replica is a 3.4x sight. I have one mounted on my CA M15A4 rifle, and I don't find it to be too much at all. I've had the sight on my TM M4A1 as well, and IMO, it worked out great. I'm sort of torn here between sticking with the iron sights (I kind of like iron sights) on the M4 and using the Elcan on the rifle, which is more than likely going to be my main gun for outdoor gaming, in which which range is more important. But in the end, I think I'm going to end up with an Elcan sight for both guns, and will swap the sight / handle on the M4 as needed. I just really like the look of the Elcan sight.
Now, anything more than 4x magnification I could see as a bit of waste on an airsoft carbine or assault rifle. On a sniper rifle, I can see it being useful, but not on an assault rifle or carbine.