I find the 89 to be a huge leap over the 83 entirely because of the screen UX. On the 89 it would draw the actual fractions and show exponents in superscript r

I find the 89 to be a huge leap over the 83 entirely because of the screen UX. On the 89 it would draw the actual fractions and show exponents in superscript rather than only using parenthesis. You could also scroll up to previous entries and bring them back to the editor (or get previous answers). The mistakes you avoid from not having to count parenthesis and being able to easily access previously typed equations was really helpful.