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.
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.