I think this sums it up. Though I give an exception if the plane is delayed and there are people with short connections. You can tell from the look of fear in their eyes as they push past. I'll make way for people in that situation and tell them good luck in making their next flight.

But if you just get up and run forward as soon as the ding on every flight? You nailed it - the only rules your are breaking are unwritten, but you're being a bit of an ....

I always get an aisle seat. I am always the first person to stand up in the aisle the very moment the chime goes off. I pull my bag up from underseat as I stand; the rare times I put something in the overhead I pull it out quick and then I take two steps, backwards.
No one behind me goes off before me, or anyone in my row; no one ahead of me goes off after me. I watch people's eyes around me looking longingly back to their bags in the overhead. "Is this yours?" I get it out and hand it up to them.

I think a bit has to do with personality. I'm first off the airplane on at least 95% of my flights...probably OCD. IMHO proper etiquette is...

1. No jostling past people.
2. Ok to move forward if no one is in the aisle or there is a clear path.
3. Let people move back to get bags they had to store further aft.
4. Help old ladies getting their bags down.
5. If you're in the aisle seat with a tall/large person on the window, get up right away so they can get out into the aisle and stretch.
6. If you can get up early and get your bag out but choose instead to sit until the last moment and then hold everyone up while you get your bag down, you're a sociopath.

What if someone wanted to get up early, but didn't jump up in the microsecond until someone following your rule #2 moved forward into the space they were going to get up into?

You can't have it both ways, unless you believe in "I'll do what I want and to heck with everyone else."

In other words, before you move forward into seemingly free space in the aisle ahead of you, you should wait a decent interval to make sure the folks in the seats next to that space really plan to remain in their seats for some time. Many people would rather sit than stand when they have a choice. They shouldn't be forced to stand to defend their turf.

Exactly. Again, folks doing this sprint to the front benefit themselves while causing a net slowdown for the population at large.

This, I don't get. If I'm sitting in row 30, but walk to row 20 and wait at row 20, it doesn't slow anyone down, given that I have my stuff and am ready to go when the aisle clears. The "flow" of people is constant, no matter where my starting position is.

On the other hand, if a person is sitting down until the aisle clears, then gets up and takes time to get their belongings, the "flow" of people stops. Again, the location of said seated person relative to their seat assignment is irrelevant.

What I don't get is people who stand up (especially those in middle or window seats) and stay hunched over due to the low clearance, for 5-10 minutes waiting for those in front of them to leave. What's the point? I just sit until the couple of rows ahead of me are actively leaving.

Deplaning behavior has worsened in the past few years. The correct etiquette is to remain seated until passengers within a few rows forward are walking to the exit. If you must stand, do not clutter the limited aisle space with luggage. Do not touch other people with luggage. If your bag will hit other passengers by removing it from the bin, then do not remove it from the bin. When your row is moving, you may then gently remove your bag. Do not put your luggage on other passengers seats.

(Same goes for boarding and flying -- do not make contact with other passengers nor other passenger seats, neither with your body nor your bags)

Lately I have observed many aisle passengers blocking the aisle with rollaboards even before the door has opened (they should be left in the bin until each row is moving to exit.)

Because of this poor deplaning behavior and TSA incompetence and overhead bin boarding wars, I think the lifespan of full-sized rollaboards as cabin bags will be curtailed soon.

Relieve aching back and knees.

Are you kidding. It would take and hour to empty the plane if everyone did this.

This is simply not true. When a person stands in the aisle, anywhere in the aisle, that person blocks other people from standing up to get their stuff. That's an objective fact that has nothing to do with rushing forward. In the scenario you describe, you have chosen to block (and hence delay) people sitting on the aisle in row 20 rather than those sitting in middle/window seats in row 30. Since aisle passengers in row 20 would normally deplane before middle/windows passengers in row 30, blocking them delays the entire process by more than you would have had you stayed by your own row. What's more, by blocking all of row 20, not just the middle/window passengers in that row, you contribute to still more delays because row 20 passengers won't have a chance to begin the deplaning process.

It's still your right to behave rudely, but don't fool try to fool us about the consequences. We didn't all just fall off the turnip truck. (If you want to fool yourself to make yourself feel better about your behavior, go ahead. We all have our little failings.)

Yes, it's THAT bad. I have seen people doing that and my reaction was "What the..." You are not pushing people physically, but you are taking up the space available to the people up front. Yes, that's cutting in line, simple as that.

To simplify to the maximum: you are now blocking passengers in row 20 from having the opportunity to deplane in an orderly fashion. Thus, when they do finally have the opportunity to get up, they will be blocking everyone behind them for a longer amount of time as they retrieve their belongings.

No increase in time.

The bags are still "ready to roll" once actual forward movement is possible.

The key thing to remember is that single-aisle aircraft are also single-file. One person is the front man in the aisle both at boarding and also at deplaning. It does not help anyone (except the occasional personal injury lawyer) to move baggage around until you are almost ready to be that single-file person moving forward.