Sydney mate
I did not go back as far as the Amiga days , as my first OS was a DOS 6.2 and I am hesitant to take OS class during my undergrad days
IF you are talking about loading OS within seconds, well actually the system I built a while back can load Windows XP Pro within 11 seconds time [normal untweaked , cost AUD 3k a year ago
] and its about the same time my Axim X50v load from a reset.
Sure you can have closed system like before, but for consumer market that move is not feasible now as people love to load everything nowadays.
Maybe you can see Xbox as a sample of a closed system OS and see how 'upgradeable' that beast is.

I did not go back as far as the Amiga days , as my first OS was a DOS 6.2 and I am hesitant to take OS class during my undergrad days

IF you are talking about loading OS within seconds, well actually the system I built a while back can load Windows XP Pro within 11 seconds time [normal untweaked , cost AUD 3k a year ago

Sure you can have closed system like before, but for consumer market that move is not feasible now as people love to load everything nowadays.
Maybe you can see Xbox as a sample of a closed system OS and see how 'upgradeable' that beast is.