Honest question but who would need this these days? Would this calculator still be useful for professors/mathematicians/etc or is this more for HP calculator enthusiasts?
I work in industry automation and use for every day calculation mostly my HP 35s, even I also have a HP 50g under my desk and more than a PC on my desk.
It's just for me the most easy way to calculate things with current and power for everyday use.
And .. even the basic Windows calc app is so slow to start, I already finished until the app started.
I have a 35s as well; I was made fun of for using one (you know you're sitting at a calculator that is 1000s of time more powerful right?). I still use it.
Just as a fun fact, some of the largest tractors made these days actually rival F1 cars in horsepower output. John Deere 9RX goes up to 913 HP for example.
My HP 35s sits between the 2 halves of my split keyboard. I use it multiple times per day. It's just faster for quick calculations as the UI is very well done and it turns on instantly.
I bought a 35s and found the ergonomics not as good as my old, dead 11C. So I bought an antique 15C on eBay, and it sits right by my keyboard all day.
I'll use the built in calc in macOS Spotlight for many things, but plenty of times each day I use the HP. Example: yesterday I calculated an angle in degrees by reading off approximate x, y coordinates from a graph on my screen. Swapping windows to a calculator app, repositioning them to see both at the same time, just too fiddly, and clicking the calc app moves the cursor so I have to remember the numbers as I switch context.. The physical HP in front of me leaves my screen undisturbed. Easy.
It's probably not a necessity - I'm sure I could adapt to just using my smartphone if I put the time into learning some of the math apps. I still use my ti-89 for everyday calculations. It's a handy device; more portable than a laptop, and better UI than a smartphone. I don't deny myself from using a tool I like.
Good question. I still use an HP42S these days, but it's an app on my phone or desktop not a separate device. Replacing batteries was a big pain on the original.
It's just for me the most easy way to calculate things with current and power for everyday use.
And .. even the basic Windows calc app is so slow to start, I already finished until the app started.