A blog comment from Hami, a NASA engineer:
I use HP calculators every day at work at NASA and the HP 35s is a disappointment. The basic functions are all there but anyone can do that. The programmable features are a kludge. Why can’t they bring back the HP 42S? The program labels and Solver were simple and easy to use on the HP 42S.
Yep … HP missed the boat again. If you don’t believe me check out the going price for a second hand 42S on EBay. I will give my newly purchased HP 35S away as a graduation present and fight to get a good old HP 42S off EBay.