I’ve never had trouble with the TI-89 UI. I definitely like it way better than the TI-84 and similar ones. It’s kind hard to compare the ease of use to the HP though because I’ve had the TI for almost 10 years and have only been using HP calculators for like 1.5 years, most of which was with NewRPL on a 39gs which was quite different from the HP UI on their actual RPN calculators.
I’ve never had trouble with the TI-89 UI. I definitely like it way better than the TI-84 and similar ones. It’s kind hard to compare the ease of use to the HP though because I’ve had the TI for almost 10 years and have only been using HP calculators for like 1.5 years, most of which was with NewRPL on a 39gs which was quite different from the HP UI on their actual RPN calculators.