> The neat part is that the first stage kernel boots in roughly 1.5 to 2 seconds. It's not really appreciably slower than other boot methods while at the same time exposing a substantial amount of pre-boot functionality.
That sounds 1.5 to 2 seconds slower than just having efistub in your main kernel image, which honestly is a LOT. Of course not possible with problematic drivers like ZFS but then you don't have to use those.
Yes, and then your main kernel image is no longer on ZFS and you lose the ability to reliably roll back your root dataset. Everything is a trade off. I reboot my workstation once a week for a kernel upgrade, so an extra 2 seconds of boot time isn't even a consideration.
That sounds 1.5 to 2 seconds slower than just having efistub in your main kernel image, which honestly is a LOT. Of course not possible with problematic drivers like ZFS but then you don't have to use those.