I think that Primarymachine is doing the mill, and I'm sure there must be others.
I believe that RDS on handgun will become ubiquitous in the relatively near future, just as they have on rifles and carbines. The amount of research, development and competition in this area is incredible. The greatest challenges seem to be coupling durability, battery life and ease of battery change at this point. A wider field of view should become a reality too as things develop.
I believe that the utility has already been demonstrated. Instead of having to have a hard focus on the front sight, the shifting of focus from the target (threat) and back to the sight before breaking the shot ( it's only milliseconds I know) the RDS allows us to focus on the target/threat and know we can break that shot when the dot appears. This was a "lightbulb moment" for me LOL. So, to me at least, this means the RDS system is just as viable up close and fast, and they markedly improve my accuracy at distance where you would have the luxury of time in sight acquisition.
In my experience the S&W Shield, Glock 43, PPS, and similar sized pistols are capable of very good accuracy at extended distances... the standard iron sights just aren't as conducive to such...at least to my aging eyes.
Lasers offer similar capabilities, but from limited experience can easily "wash out" in bright outdoor lighting. YMMV
I am not in any way being argumentative nor dismissive of what @hipower is saying, and I admit "learning" a Red Dot initially takes a bit of practice (Dry fire is your/my friend )... but so did initially learning to use iron sights. And I agree, most defensive use is definitely relatively close. But having the ability to engage the most statistically probable event plus the outlier like an active shooter event can't be a "bad thing" in this day and age.
My apologies for the drift/tangent. I'm looking forward to what develops and look forward to hearing of others experiences.