I've been using those since internal routing became a thing. They work great and tend to last about a season. I keep a couple of extras in my tool wrap just in case. I've gone internal on my last two trail bikes because I've gotten used to strapping bags onto the frame now and I hate it. I like being able to pull off a brake to gravity bleed it or swap them between bikes if one goes down.Yes! I don't plan on routing a rear brake cable though a mtb frame ever again. Such a PITA for no functional gain.
I don't know how good they are, but I recently bought some stick-on (or zip-tie on?) external cable guides for a future frame.