I've messed with them off and on. They are not real cheap depending on the type of sight you want and the mount you pick, from around $100 up to $400 if you wanted a really nice set up.
I didn't like it because of the expense (and a had a cheaper one), they can be heavy and bulky compared to a normal 3 pin sight, you have to rely on a electronic device with batteries, you are limited to one pin and other things I'm sure I am forgetting.
Oh, they can be a pain to set up properly as well.
I have played with many different sights and I always come back to the good old inexpensive simple 3 or 4 pin sights. Light cheap and rugged always seems to work well for me

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This subject comes up every now and then if you want to do a search on it there are a few threads about. Some like them, some hate them, and others like me are indifferent. And some think they are only good for shooting in the dark and poaching.
Paul