Somehow the TI-89 had _both_ snappiness and relatively advanced 2D math display.
The TI Nspire CAS is the pinnacle of calculator UX, though - crisp , large, and hi-density LCD, beautiful math formatting, and dedicated alpha keys. I’d rather be doing symbolic stuff with that. In college physics it saved my ass by doing unit analysis on my answers as a double-check, converting units to base SI units and then doing as much simplification as possible.
The TI Nspire CAS is the pinnacle of calculator UX, though - crisp , large, and hi-density LCD, beautiful math formatting, and dedicated alpha keys. I’d rather be doing symbolic stuff with that. In college physics it saved my ass by doing unit analysis on my answers as a double-check, converting units to base SI units and then doing as much simplification as possible.