I've only tested it, but i noticed a few nice things. It has a fairly wide field of view. Feels fragile at first (actually the little lens cap on the front broke installing the thing) but if you get it put on well it's quite stable. Warranty against damage anyway, so who cares. Red dot is excellent. Has 2 settings, but even the first one showed up fine in the middle of the day, unless you point it at the sun, but why the heck would you be doing that?
Has a fragile feel. Doesn't fit very securely onto a flatline barrel system, but that's the barrel shroud's problem, not the sight. Also, if you have a flatline and you get the sight, you're gonna have a problem with your hopper blocking your view. I'm gonna see if I can solve that with a new elbow or an extension. Also, getting a smaller 40 round hopper may be better. If you're sniping with a sight you probably don't need more that 40 rounds anyway.
I noticed you have a collapsible stock and so do I. I'm looking into purchasing this item for my Custom as well. I'm just wondering, when your wearing a mask and using the stock can you see through the sight or do you need to purchase a raised sight rail?