Anybody use them? Are they worth getting?

I bought one and found it to be useless. It is a pinpoint accurate device being used in an area-impact weapon, and the sighting system on most shotguns isn't precise enough to make use of the laser dot on the target. Save your money. I use mine to tease my cat.

It would be easier to just pattern the shotgun to see where is shoots relative to point of aim.

For slug shooting they would be ok, In fact I have one I've never used. For shotshells? Like the others have said. Pretty much a UPS

I've used one on my Browning Gold Deer hunter which has a rifled barrel I use sabots in and a Nikon scope. It has almost rifle like accuracy within a reasonable distance so is worthwhile as sabots are expensive if it takes quite a few to get sighted in.
BTW don't buy a cheap bore sighter. I did and found it worthless and took it back and both a better one.

This would be a waste of money on a smooth bore weapon. Even with good Foster slugs you'll be doing good to hold a 7-10" MOA at 70yds using a red-dot.

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A couple of years ago I used a low priced one.

Intended targets were coyote and feral dogs.

We were allowed to hunt coyotes after dark at the time.
Hoped the red dot and #4 Buck would solve the problem.

Coyote and the feral dogs never showed up when I was in position.

Well Ihave to disagree on the 7 10 inch thing. Way back when I had a Weaver Quick Point in a sidesaddle mount. On a variety of shotguns with Foster slugs it would easily shoot under 3 inches at 75 yds. But they were all open choked guns. In fact had a Marlin 120 with a smooth bore slug bbl that stayed under 2 1/2 inches with ne of those Quickpoints. Heck IIRC they were the only red dot sights out there for a while. Didn't work in the dark though.

I'd be using it for a 23" cantilever slug barrel with a 3x7 scope. Was hoping to limit the number of sabot slugs I have to use to sight in.

It might be handy for head shots on turkey or other game that might stay still for a few seconds.

Most of the good shooters, do it the old fashioned way.

And for that use it will probably do just fine. Many of those bbls will shoot sub one inch groups at 50 yds I don't think the OP was looking for a lazer sight in tool for shotshells. but even for a tight choke on a turkey gun the lazer sighter may do quite a bit of good. with a red dot sight or low powered scope. Some people use a low powered scope for turkeys so I understand. Some of those sabot slugs are 3 bucks per shot.

Haa haa, while I'm a good pistol, rifle and shotgun shooter, I've never used a scope before! This siting in with sabot slugs will be a first for me, so I wanted to limit the wasted rounds factor of fiddling around with a scope as much as possible.....

My first rifled barrel slug gun was a Mossberg 835 with a cheap scope I later regretted.
I didn't have a bore sighter for it and started shooting expensive sabots at a target about 50 yards and trying to fine tune my hits as I wasn't too far off initially. Having a brain fart I was turning the scope adjustments in the opposite direction and kept getting off even more. By the time I figured out my error and turned in the right direction I'd shot up a lot of expensive sabots and had a sore shoulder.
Another good use for a bore sighter is to check zero on a gun without firing it. I used to take my Rem 700 deer hunting up north and after getting there I'd use my bore sighter to check my zero without having to shoot it. It never was off but did assure me it was still on after maybe bouncing around in the back of my CJ-5 a long trip and over trails to camp.