Yes, I have the Holosight XLR mounted on the AR-15. As I mentioned, if the brightness is dialed back the dot comes into better focus but one can still lose the dot in some light conditions, particularly when the lighting is varied between the shooter and the target. I have a 1 MOA red dot sight and it is better for accuracy than the more common 3 and 6 MOA dots but still not the equal of a simple 2x scope. It is probably better than iron sights and thinking upon it, I would say a large part of my opinion is based on a difference in need and training. I use an optical sight for rapid target acquisition rather than short range precision. This is the way I have been taught and I choose and use other tools for precision work. If you can find a red dot with a recticle no larger than 3 MOA (and smaller would be much better), then you might find it to work well. After all, at 50 yards the dot would only cover an inch and a half and that should be not be too much bigger than a squirrel's head at that range. Of course, the problem then is if only a portion of the head is showing, there still may not be enough visible to get a decent sight picture.
For the cost of a Holosight ($250+), one could easily pick up a red dot of some type and a scope, plus some rings for each to compare, and still have money left over for a scoped pistol holster and some ammo to compare them with.
I prefer the tubed models that look like a standard scope versus the HUD types as they fit in a holster much better. TruGlow, Bushnell, Millet, and even BSA have a few models that should work. These are under $100 and often come with rings. The BSA 2x handgun scope is a decent value and I have seen them in the $70 range without rings. One of the better places I've found for optics is Natchez Shooters Supply at
www.natchezss.com. There are other places but this is one I'm personally familiar with. Take a look at them online and use to help compare costs and features.