@ ALMKLM: What you asked for (and more, more, MORE! than you wanted!)
I looked up a couple of bikes. For me, comfort on hills is it. If I dont' have the high gear I want, it isn't a big problem. I need my low gear.
I'll use 18th Street as an example.
http://www.trekbikes.com/us/en/bikes/urban/allant/allant/
48/38/28 front and 12-32 7-speed rear.
457% gear range
This would be typical of most 21 or 24 speed bikes. For me, the low (28/32) isn't quite low enough - and it is a really common low gear. I could get up 18th, but I wouldn't like it much.
A bike shop dweeb famously told me a week after I did the DC trail round-trip "It will be low enough once you get into shape." Which I think is kinda true for most people.
I would prefer what Salty has on his mountain bike
24/36/46, 13-30 rear,
442% range
Low of 24/30 - it's like half a gear lower than the Trek. But that half-gear is such a difference on all these cliffs they pour asphalt down and call streets around here.
I like to pedal lazily down hills sometimes at a low cadence. With Salty's mountain bike's highest gear, I'd either have to coast or work (higher cadence) going down 18th.
The smaller wheels make it slightly easier on the up hill, and slightly less power going down. But the wheels don't make too much difference.
Salty's road bike:
30/39/50 12-25
347% range
The high is good. Low of 30F/25R? I'd usually be walking up 18th. If I didn't my legs would burn and going slowly wouldn't help. I want not just one but two lower gears.
I would recommend against this as a commuter bike, and hope I don't p*ss Salty off, because I like him.
Kayla's and Nick's bikes.
30/42/52 12-25T
361% range
The high gear? 52/12? That would be NICE cruising down 18th. The range is decently wide, but too high for me. Not unusual Same low as Salty's road.
Gary Fisher Mendota (I dont' know this bike at all, just picked it from the 'net. Looks nice.)
http://www.trekbikes.com/us/en/bikes/gary_fisher_collection/fast_city/mendota/
48/36/26 11-26 9-speed
436%
I would NOT consider this bike for me, because it has 27 speeds, but not the one gear I use the most. (nor the next one up)
Plenty of people here would have no problem with this gear range though and might think me crazed for wanting one lower.
Surly Long Haul Trucker.
http://www.surlybikes.com/bikes/long_haul_trucker_complete/
48-36-26t 11-34 9-speed
571% (! ! !)
That bike has some GEARS on it. All of it is good.
Internal hubs The Shimano 8 speeds have about 310% range, which is OK at best.
They irritate me because they have small shifts between the highest gears and big shifts between the low ones. I want the opposite.
I just saw a 9 speed SRAM with 340% gear range.
http://www.sram-imotion.com/us/html/navigation_us.html
Looks like an OK set of gears. I like the little 14% jump between the first and second gear. Don't care for 14% between gear 8 and 9, but no biggie. I could have 28% between the upper gears, no problem.
The Rohloff 14 gear has a range of 524%
http://www.rohloff.de/en/products/speedhub/gear_range_comparison/index.html
CAUTION. Some bikes have one super big cog on the back. This looks good at first. "I'll have my LOW gear!" But the shift between first gear and second gear is so intense that you find yourself always wanting to be in the middle. That shift between first and second is important and you dont' want it much more than 20%