I have sent them a couple. They do excellent work. I am very pleased. The guns are beautiful. It is kind of pricey, and they take a long time, but the work is high quality and you will end up with a gun that looks like it did when it was first issued.
You can buy a junky grade shot out CMP gun and send it to them to restore, and it will come back like new, and that actually saves you a good bit of money over just buying from them. There is no reason to send them a service grade. And don't send them anything that is extremely collectable... restoring might reduce its value.