My latest experiment is taking place on plastic Trek frame I picked up in a barter deal. I had a pair of TA 150 cranks that used to be on my kids' Cinelli BMX bike, so I've put these on the Trek. I'm running a 45/17, which gives a gain ratio of 5.9, just a bit higher.
When I first get on the bike after riding with longer cranks, it feels a bit funny at first, but within a very short distance it's just fine. I go just as fast, climb just as well. For a given speed, my pedal rpm is higher (though my pedal speed is the same) but the short cranks make it easy to spin much faster than I normally would.
After riding this bike for a few miles, when I get back on "normal" cranks, they feel a bit weird and long at first, then I get used to them after riding a couple of minutes.
I think people really obsess too much about crank length. After all, we all use the same staircases, whether we have long or short legs. Short legged people acclimate their knees to a greater angle of flex to climb stairways, and can also handle proportionally longer cranks than taller people normally use.