How would you rate your keyboards?

[Helix]

Evaluating a keyboard is certainly not easy, because as stated in another thread, keyboard preference is a subjective thing. Furthermore, when we say that a keyboard is "good", "very good" or "excellent", we implicitly make a comparison with other keyboards. But we don't have the same calculators to make valid comparisons. For example as far as I am concerned, I've never used calculators like the HP Classic, Woodstock, Spice, or the HP41. Perhaps I don't know what I am missing.

My main concerns are reliability and pleasure to use.
Here is my ranking of keyboards:

10/10: HP 15C
I borrowed briefly this strange calculator to my neighbor when a was student, and I remember two striking features : it was very difficult to use (I was not familiar with RPN !), and the feeling of the keys was… impressive!

9/10: HP 48S, 48GX
Excellent keyboards, but they didn't give me the same feeling as the 15C. Perhaps my memory of the 15C is not accurate.

8/10: SHARP PC-1401
Very soft keyboard, no clicks, but reliable and pleasant.

7/10:
HP 50G: very good keyboard, but exceptionally, I get a double entry with a single press. I would rate it 8/10 otherwise.
HP 200LX: the keyboard seems fragile, but works very well.

5/10: DM15 (credit card format)
This is a special keyboard, as it is best used with thumbs. Not very pleasing nor effective, but very reliable.

3/10: NP-25
The small keys are uncomfortable and not very reliable, especially after several months of inactivity. I wonder if some corrosion develops inside. Of course, it is not designed to be a daily calculator, so I'm still satisfied with it.

0/10: TI 57 LCD
I think it's impossible to make a worse keyboard! Totally unusable after three years.