I may have jumped the gun. I was assuming PXE to boot an imaging environment, which copies the system image to local media so you don't have a runtime dependency on the boot infrastructure. In that case, speed-wise, you've not gained anything because you've got two boot cycles and a system copy before your new server is ready.

If you're not copying the system image and simply network booting a remote image, then that doesn't apply, and yes, that can be fast.