I think today we have about the same booting time we used to have 25 years ago with MSDOS on an XT or 286. Which is not that nice. Currently I'm a little sceptical about that 5 second boot: it sounds great, but we have to add the BIOS time, the grub timeout, the time of getting IP address via DHCP, etc. I'd be pleasently surprised if we'd managed to get a working desktop 20 seconds after the power button have been pressed. On the other hand I'm sure that there is bloat that could be trimmed down.