Long Zheng of istartedsomething.com has posted a good explanation of why Microsoft opted for the honeycomb user interface for Windows Mobile 6.5. It boils down to finger shapes and how to most effectively layout circles.
First up, fingers.
Contrary to popular belief, the tip of human fingers is not squared, but in fact circle-shaped when depressed against a hard surface like a touchscreen. When you’re space-constrained as you are in something like the applications menu – where there’s a fine balance between how many icons can be displayed at one time and how easy it is to hit the icons, large circular hitareas makes it easier for users to touch the desired icons and avoid accidentally hitting nearby icons.
Then there is the idea that an orthogonal layout is more efficient for circles than a simple grid.
The mathematically most efficient method to arrange non-overlapping circles – a problem called “sphere packing” – is actually and as you might have guessed by now, hexagonal.
Combine the two and you can start to see what Microsoft was thinking. We’ll know when we all have Windows Mobile 6.5 devices in our hands just how right Microsoft got it.