Addition of a training mode for operators, symbols, fractions and exponents would be very useful.
I found having to train myself to write in way the calculator understood rather than training the calculator to understand my writing 180 degrees off from my expectations for a handwriting interface application. Pi was the most troublesome of the symbols. I get 80% recognition of pi now on my 5800. With numerals, a misread is so rare as to be remarkable.
This is a wonderfully useful program and will so replace the usual calculator on the N97, the 5800 and all other S60 touch screens in the future. Good work folks!