here are a few I thought of:
"Designed for the computer age"
"Travel less, type more"
"The natural layout"
"Statistically Better Design"
"Modern, Unique, Easy"
"Fast, Accurate, Easy"
"The better choice for typists"
"Learn it, Use it, Love it"

yeah, I like that one too, it sounds professional, describes what it is about (typing), easy to remember, to the point, etc....

or it could sound like travel less (to the doctor cause of wrist pain)...lol

i think "travel less, type more" is the best one so far
I'm not sure i like the word TRAVEL though
I don't know about you guys, but when I think of traveling, I think vacations and beaches and sightseeing... not something I want to have less of...

well here's a version  that mentions health, finger travel without word travel and important keyword 'typing': 

"Less finger moving, more ergonomic typing"

if not moving, then maybe roaming?

"Less finger roaming, more ergonomic typing"

"More Typing, Less Distance."

"More Typing, Less Leaping."

How about "Less distance, more typing." its so unique...
(notice lower case letters...) :P

I was trying to think... whats a word for like... going back and forth....... flip floping... like a fish... reciprocate?

stay simple guys! remember, it's for cave men...

As for "better by design", there's still a number of results when you use quotes.  I'm sure I'm not the first person to put those three words together in that order.  Slogans don't have to be unique, just effective.  Anyway, it was a suggestion about a direction we could try that didn't involve fingers.

Many good thoughts here. I liked "Take miles off your fingers". Most of our suggestions so far don't show people why the hell they should take the pains to install Colemak when they already have Dvorak in their computers though?

"Colemak – the improved layout for a new millennium!" It's a bit long but I kinda like where it's going. (The hecklers will say that soon enough in this millennium we'll all be mindlinking or at the very least using voice input only, but I think they're wrong. I work in mind research and getting any specific output from the "bowl of noodles" without training a lot is very hard to do; it's all so general. And voice input isn't as convenient as people may think. I like shutting up and typing, haha. Yes, we'll probably end up mindlinking but it's at least 50–100 years ahead before it works well in my rough assessment, which gives us time to use slogans with impunity in the meantime.)

Colemak. The new black.

Do your keyboard a favour: Colemak.

Love your fingers. Colemak.

(It seems that in the name of advertising, "Colemak" can now be used as a verb. That's nice.)  :)