Just from personal experience, Android always reports my display as consuming the majority (around 60%-70% usually) of my battery, anytime I've cared to check. That's for general usage as a phone/music player.
Hmm. My screen's been on for 2h 22m out of 2d 10h 22m (about 4%) and it's used 3% of the consumed battery. 49% of the consumption is cell standby, 47% is phone idle.
YMMV of course, but 70% screen consumption seems way high to me.
I guess I don't check except when I'm low, and if I'm low, it's due to using it and having the screen on. If I leave my phone "off" (that is, I don't actively use it, but the radio is on), then the display is less (for a N1 I have on me, it says screen is 20% this morning, and it's done nothing but sit there for a day).
In other news, the light bulb in my refrigerator is always on, anytime I've cared to check.
In other words: chances are that you only check power use when your display is on. If the display is off 80% of the time and all other components stay on full time, that would sink the power use of the display to around 25%-30%.
Your comparison is flawed. The Android power meter shows the power consumption that has happened over a period of time, not just what is consuming the power the most right when you look at it.
If I disable WiFi, then check the power consumption, WiFi still appears to be consuming approximately 4% of the batter compared to 42% by the screen, which is the top listed item, and dwarfs the number 2 item, Android OS at 9%.
If I run without WiFi for a period of 24 hours or so, then presumably the WiFi battery consumption would drop to 0%, or at least begin approaching 0%, but either way, this is a far different test than just seeing if the refrigerator light is on.
The usage report is cumulative, not instantaneous. The act of checking probably isn't a significant fraction of their phone usage.
So if for a given usage pattern the screen does consume 60+% (which is what I often see) then keeping it off all the time certainly helps ... but also makes the phone a lot less useful!
Those other components don't take much power. My phone lasts a week idle, and the hours it lasts with the screen on would go up tremendously with e-ink, especially outdoors. The backlight takes an overwhelming majority of power for such activities.
The big problem with that Moto phone was that it was using a segmented e-ink display, like a e-ink calculator screen. So it could display phone numbers well, contacts poorly, and texting was a joke.
Samsung had, er, this thing in 2009. (http://gizmodo.com/5251232/samsung-alias-2-e+ink-flip-phone-...)
People complain about input lag - see some of the comments about the Mozilla firefox phone. I guess they'd hate the refresh rate of the eink.
And isn't a lot of the power going to WIFI or 3G, rather than the screen? How much advantage is there?