"If your port goes ... Hunh?"
Poorly worded on my part? If the monitor on my iMac croaks, exactly what good does it do me that I've got a port I could hang an external off? I've still got to send the whole iMac back to be repaired. ACD croaks, I plug in a spare monitor while the ACD is off being repaired.
I can certainly understand why AIOs are a nice solution for you. What I can't understand is why you seem to think the reasons AIOs are not the right solution for others are so marginal.
For you, hanging external optical drives, etc is fine, apparently (although I have a hard time reconciling that with the cable and clutter argument). I suck it up and accept it, but it's second-rate in my world. Can I cart my iMac to an Apple Store and have them charge me a 500% premium for a new drive? Sure. But I'd rather order exactly what I want, have it delivered to my door overnight, replace the thing myself and skip the drive, the hassle, and the ripoff charges.
At any rate, I wish you seemed as supportive and tolerant of others' balance of the various aspects of ownership as we are of your own interest in not being straightjacketed to a noisy case, cables, crawling under desks (speaking of thin gruel, seriously, how much more frequently do you crawl under desks of your towers than your AIOs?), etc.
p.s. It's great you've got the old G4 in service as a file server. But surely you'd admit if it was tied to the ACD, you'd have lost some benefit from the ACD, that you still have as things stand.