It's pretty spot on. As long as you have the right hole saw and you have the angles right, the miters fit up really well. The cuts themselves take about 30 seconds. Depends on the angle you're cutting at and the size of the tubing and the size of the hole saw. It probably takes me a little longer since I stop and lubricate periodically to try to extend the life of my hole saws. Otherwise, a minute with a file to clean up the burrs and you're good to go.

I notice you're in Palo Alto. If you're in the city anytime, feel free to stop by and take a look. I'm close to the SF Zoo.