I don't have one and wish I did. My dream would be to have a prewar .38/44 Outdoorsman so equipped, and with thumbrest Ropers as well. A .38 M&P Target model with a King rib sight would also fit in my safe.
I would expect the sight to add at least 10-15% to the value of the gun alone, and I wouldn't be surprised if the owner asked more.
I also know some people think these are ugly monstrosities. That's fine -- the reduced competition will keep the price from rising higher for those of us who like them.