I have a WTO built rifle w/ a SwitchLug on it. I haven't yet had a second barrel spun up for the rifle, and haven't bothered to test out removing the barrel and re-installing it. Been having too much fun shooting it... ha ha. I have no reason to doubt that it works like they say - I just haven't tested it, so I can't speak from personal experience.
One thing I don't see people mention with this setup is that it sort of gives you the best of both worlds in the current 700 style action switch barrel situations. Once the lug is installed and your smith has dialed in your first barrel, they can take a headspace measurement and use that later to spin up additional barrels without having to have your action on hand. If done correctly, you can essentially order a pre-fit barrel from your smith and install it, without a need for go/no-go gauges or a jam nut. Again, I haven't tested this part of the functionality, either. I believe the measurement taken is from the bolt face to the front of the lug, but I may be completely incorrect on that (so if that doesn't make gunsmithing sense, just ignore... ha ha).
This feature was my primary reason for getting the SwitchLug included on the rifle. I may end up buying a .223 bolt (it's a Stiller TAC30A/W action) and having a .223 "trainer" barrel spun up at some point, as well, so it would serve that need, too.