ti's current top of the range model.
this is quite simply the most impressive calculator i have ever seen.
for a machine of this complexity, the choice of keys is very good. the
keycaps themselves appear to host strange and rare things, but in fact,
these are the things you need when working with formulae. for example, x,
y, z & t are on keys of their own, other letters are on shift keys.
formulae mostly involve these variables so it make sense to put them up
like this (unlike hp).

standard scientific functions are also on the keyboard, albeit on
shifted keys, but at least they're not hidden away in menus (like hp). the
problem here, is when a calculator acquires the ability to perform rare
and wonderful functions, you must not lose track of the fact that the
mostly needed functions are still the simple ones and they need to be
accessible.

the drop down menus are easy to use with the f1-f5 buttons and the 4
direction keypad is just great to navigate the screen, scrolling and even
cut and paste from previous expressions into the current one. which i like
a lot. although the case is somewhat plasticy (hp wins here on build
quality with the 48g), the rubberised buttons work
well and feel positive. note here that its a different story with some
cheap ti's like the ti-30xbii.

calculation in general and symbolic operation rocks, humiliating the hp
offerings. for example, general (numerical) calculations are first handed
to the symbolic engine and then numerically evaluated. this makes for
partial simplifications and greater accuracy. this works well for stuff
like solving and definitive integration where the integrand sometimes gets
modified to accelerate the numerical process or sometimes solved analytically
for a complete symbolic answer. check some out in the torture
test. even raw numerical accuracy is excellent. its also fast.