I'm using one on my current project. I just finished inletting it. Not nearly as easy as a conventional side lock to inlet because the lockplate is stepped. If I had to do it over, I would move it farther back towards the breach. I had to make a small notch on the bottom of the breachplug lug to clear the tip of the mainspring and the link that connects it to the hammer. I installed a conventional rifle nipple where I would normally but the vent liner.
The lock seems well made and properly hardened. Only a couple of moving parts. I'm eager to see how she shoots.
If you decide to use one, be careful with the layout to make sure the mainspring clears the breach plug.