Are the new buttons .5" by .5" or so?  That is my best guess.  Can you
really hit those without hitting other buttons by mistake?

i don't know the exact measuements, but if they're the same size as the 
prototype from maker faire, then you need really large fingers (like, 
REAALLY large) to accidentally hit some extra buttons

this user had problems with the button size
http://www.youtube.com/watch?v=jBvIMK2K2Lo
but I think I'd blame it on extensive exposure to radioactivity than 
anything else.

> extensive exposure to radioactivity

Gamma rays, to be precise.

40h buttons are .5" square

new series are .4" square

i don't believe there will be problems with mis-pressing. they're 
separated by .2" and like any instrument/tool, you become proficient 
with practice.

i'd honestly never really considered mis-press to even be a potential 
problem at this size.

Awesome, thanks.