"Spy shots have been floating around the web of a new honeycomb-style launch screen in Windows Mobile 6.5 (Engadget, PocketNow).
I haven't read anything official about why they chose this design, but I think it's a neat idea. Packing touch regions together in a hexagonal grid is more efficient (space-wise) than a rectangular grid, and it also makes the cells closer to circles, which means they're a better fit for our (roughly circular) fingers. Some of the descriptions I've seen call the honeycomb "finger-friendly," apparently for this reason.
Whether this benefit is provable, I don't know, but it would be interesting to test it experimentally. It probably doesn't make much difference when the regions are large like on this launch screen.
It might make a difference on a soft keyboard -- if you offset the rows you could expand the touch targets to hexagons and thus they'd be a better fit for fingers (to clarify a bit more technically: the Voronoi regions formed by a diamond grid like this are hexagons, ignoring the sides).
The iPhone keyboard offsets the rows (at least the first two), but the BlackBerry Storm doesn't." (Continued via Touch Usability) [Usability Resources]