From my point of view, problem of this approach that 'fast boot time' is the only criteria, not maintainability, not reliability, not fault-tolerance, not easiness to learn, not reconfigurability. The only criteria praised is very end-user oriented 'boot time', which actually... doesn't matter! On user machines i guess it's much faster to do suspend to disk. On servers startup time doesn't matter, you need reliability there and maintainability. So where do you need fast boot time??? I know only one application - embedded devices, but still, they may use suspend to disk, it would be also real hell i guess to debug such binary boot on embedded device.