This brief video - uploaded by Jeb - shows the remarkable difference between a normal walking-speed jump, and a sprint-charged jump! The distance a player can jump is at least twice what it would be normally, which opens up a lot of navigation possibilities! Take a look!
Additionally, Notch uploaded a picture of the updated pig model - they now have snouts!
Oh man, Jeb this is what I'm talking about. Simple additions to the game that can have huge gameplay value.
I can already imagine all the various uses for this jumping, especially with regards to ravines and the more narrow areas of them. I do hope the ravines in general are super long and wide at the biggest, but having these narrow parts and jumping is just an awesome way to get from A to B with a good amount of risk added to it.
Also, in cave systems I see multiple uses for this, not to mention overland uses as well. Adventure maps, anyone?