One of the biggest things to be careful of, when buying cheaper dot sights, is to make sure they are going to work in bright sunlight. I sucks when you go out shooting with someone, and then you have to explain to them that you can't shoot now, because your dot isn't bright enough to see against the target. What's worse is when you've traveled to a match, and paid your entry fee and then discover that your sight no worky. Fortunately, the Primary Arms sights don't have that problem. The dots in the PA sights can be made bright enough to work in bright daylight.
Blue Tint :(
When I took the M3 clone out of the box, and looked through it, the blue tint of the lenses was immediately noticeable. I didn't immediately notice the tint with the Micro clones, but it is there, though not as bad as the M3 clone.
The blue tint of the M3 clone is not a deal-breaker, as far as I'm concerned, but it is sort of annoying. The tint of the micros is barely unnoticeable
One of things you lose, over a real Aimpoint, is battery life. An Aimpoint M2 will go about 3 years, left on, on a single battery. The new Aimpoints with the ACET circuits are said to go 5 years. The Primary Arms sights will not go nearly that long, but I have not personally measured battery life.
I left one of my micros left on for about 9 days with the battery that came with the sight. When I went to pick up the rifle again, the battery was dead. I replaced the battery with an Energizer. I have since left it on for a few days, before realizing that I left it on, and that Energizer will still operates the sight just fine. So battery life is good, but not as ridiculously long as the Aimpoints.
I don't think I've replaced the batteries in the M3 clones, though I don't use the uppers that they are mounted to as much as I use the uppers with the micros. A little research shows owners of PA micros and M3 clones reporting about 200 hours battery life.
The M3 clones run on 357 button batteries (that's pretty easy to remember), and the Micros run on 2032 coin batteries (same as the Aimpoint Micros). These batteries are easy to find and inexpensive at Wal-Mart, and if you are in a pinch, at drug stores and other places that sell electronics for about twice the price, maybe more. Keep spares in your range bag, your pistol grip, vertical grip, or stock.
Primary Arms Micro QD Riser Mount
The PA micros, with detachable Picatinny mounts, should work with any mount that is made for an Aimpoint Micro. There are some Primary Arms micros with built-in mounts though. Primary Arms offers a QD mount high enough to co-witness with back-up or fixed sights on an AR-15, as long as you aren't using the Troy Micro BUIS made for the HK 416 uppers.
The sliding button that locks the lever in place has a stiff spring. The locking lever itself is rather stiff to operate also. It's not as good as the American Defense mount that I bought for the real Aimpoint T-1, but the Primary Arms mount is three-eighths the price of the AD mount, and less than a third the price of the Larue mount, so it's kind of hard to complain. The PA riser mount works, and it's very inexpensive. It's just not very slick, and it's made in China, or some such place, while most of the other more expensive options are made in America.
AK Platform Use
If you are going to mount a micro sight on an AK with an Ultimak gas tube or TWS Dogleg mount, and you want the micro and iron sights to co-witness, then you'll want one with the built-in mount (model MD-07), not a detachable mount (models MD-06, or MD-08). The Primary Arms micro with detachable mount I have on the WASR-10 with Ultimak sits too high to co-witness. The built-in mount would also probably be desirable for mounting on a pistol with a scope rail. Primary Arms Blog: Why Three Versions of the Micro Sight?
The PA micro sight that I mounted on the Ultimak does get warm after shooting a few magazines through the rifle. Although it did come loose, the heat doesn't seem to have done any harm to the sight. I haven't bump-fired drum magazines, but everything seems to be good to go.
Micro Kill Flash
One option available from Primary Arms, but not available from Aimpoint is a micro red dot optic with a screw-in Kill Flash. If you are not familiar, a Kill Flash is a honeycomb disk that hides the light from the LED emitter from everyone not looking directly through the tube. Kind of silly, for something that's not really a combat optic, but I credit PA for innovation.
I tried taking the Kill Flash from my Aimpoint M2, and screwing it into the Primary Arms M3-clone. The Primary Arms sight seems to be too small in diameter, and the castle nut holding in the front lens goes right up to the front edge of the tube anyway. No go.
If you need a red dot optic for a plinker, or even a competition gun, definitely consider a Primary Arms sight. Probably skip the Kill Flash though.
Besides the blue tint, there isn't really anything that I have to complain about. I haven't had any mechanical or electronic issues.
Durability seems very good. The lens covers on the M3-clones are holding up, which is surprising for "freebies," considering that I've had several sets just fall apart with normal use, including Butler Creek covers. The bikini lens cover from one of the micros broke, but that sometimes happens with the Aimpoint Micro lens covers too. If you look on YouTube, there is a video of a Primary Arms micro sight getting tossed around and dropped on the concrete pad of a shooting range, then picked up, and it's still working. Placed back on the rifle, it's still holding zero.
For a defensive firearm? Well, they do hold a zero pretty well. You can't leave them on, like you might with an Aimpoint, but if you have iron sights co-witnessed through the optic then you should be fine, just turn the sight on when you need it. Maybe not optimal, but workable and a lot cheaper than an Aimpoint. Don't spend ALL your money on optics, and not have money left over for ammo. Live-fire practice is important to develop the software needed to be effective, don't skip it to buy better hardware that you don't really need.
I will also caution you not to buy cheap, and then ending up buying twice. If you are going to end up with a quality optic eventually, consider holding off and saving your money. I knew when I bought my Primary Arms sights that I could always put them on rimfires or airsoft guns. The tan M4 in the photo above is actually an airsoft gun. The AR upper with the M3-clone at the top of the group photo is a 9mm upper that I bought for practice at indoor pistol ranges, and that sight isn't going anywhere.
If you think the blue tint of the M3-clone might bother you, maybe check out a Vortex sight.