But then you're back to square one, except you've made the problem worse by dividing it into 100 units instead of 5. What's "100%" mean? It's pretty clear what "0%" means (no signal), but what's "1%" mean?

100% would mean whatever equates to getting full telephony/full data bandwidth. As throughput drops, you can certainly apply a percentage to it, until you get to 0%, no throughput.

People would then learn that at x% they are getting decent data speed, and at x% things become unusably slow, at x% voice service drops off, etc..

How about just showing the bandwidth itself and then make it colored differently if it drops below the ability to make a voice call?

That's not how it works at all though. Speeds step down at different rates depending on many factors.

All the more reason to give yourself a bigger domain (101 elements instead of 5). You don't need to map into the percentage domain directly from signal strength; you could easily define a function of data/voice connectivity as throughput to a percent scale.

"But data and voice have different quality of service criteria and blah blah blah!" So make up a function that accounts for this. Or add another indicator for data exclusively and keep the bars for voice.

  you could -EASILY- define a function of data/voice connectivity
  as throughput to a percent scale.

  "But data and voice have different quality of service criteria
  and blah blah blah!" So make up a function that accounts for this.

Translation: insert magical code here?

You remind me of people who say "Your videogame is so slow, why don't you use multiple cores? Just use threads, you could easily do it."

Practical problems are rarely easily solved.

And yet this problem has not only been solved but been subsequently broken by marketers. Some things that seem easy are actually hard. I'm sure defining the appropriate function isn't all roses but a semi-competent software/radio engineer could figure out something with the right properties. With Apple's budget, they could easily do this.

Good idea. Make it a user selectable option.

Yup, that's the apple design philosophy right there.

In fact, the battery percentage option on the 3GS and the 4 allows for such a choice, but you're right that it's uncommon.

Googling around, you can toggle this feature on a 3G (or earlier) by jailbreaking the device and grabbing a third party utility called SBSettings.

signal strength is measured in logarithmic units, not linear.

And, even then, I hear that the relative metric is signal-to-noise, not raw signal strength.