Well... I'm also nostalgic on these calculators.
I owned 15 years ago a 11C. One of my class pals broke it. I was offered a brand new 15C. It was stolen. I then bought a 41CV, that I sold later when I began law studies (no need for maths anymore).
I am now a financial manager. I had a 19BII bought by the company. I bought a 41CX on sale on this site, and I was surpised to notice that I really enjoyed using this calculator, better than my 19BII far more legible and powerful. I saw the prices on ebay and tried my luck. I sold it 7 times what I bought it ! and then I felt again nostalgic, and bought two of these. What is sure is that I wil never get rid of all...
They are so easy to use, even for simple operations. On topp of that, I've got a few modules that I want to know and use.
I also had a 48GX bought by my previous company, and even if this is a tremendous calculator, it never has the charms of a simple looking 41 with all the functions hidden in the f CATALOG 0...
Well, even if i'll continue acquiring different HP's, I definitely consider that the easiest and best calculators to use ar the 10C, 11C, 15C and 41.