I am all for as simple as possible for the v0.1 release
Getting the actual calculation routine debugged and the input circuit seems a lot more important than playing with the menu system to start with.
One thing I was thinking of is since the atmel has limited writes would it be reasonable to attach external memory like a
24c164 type of chip to it and save all the data there? 1 million writes seems like a pretty good lifetime to me. I don't know if there are libraries available to interface with it, but if not it would be a lot of work and probably not worth the effort to build them.