In the past few days I have flashed my HP-20b and applied the overlay. My reactions:
1. The calculator looks fantastic! I admit that I was worried that the overlay would make it look amateurish, especially since "clumsy" is my middle name. Anyone who is holding off because they like their calculators smart should stop worrying and go ahead!
2. The firmware is astonishing! I've never seen a feature set like it on a calculator of this size. A lot of trouble has gone into making everything work well on the chosen hardware and it shows. The usability of this machine could scarcely be better. Highlights (for me) include the flexible way in which registers can be addressed, the handling of complex numbers, and the huge number of space- and step-saving programming commands. The firmware is stable (no crashes at all) even though I'm not running the latest version.
3. The manual is superb. Although it isn't aimed at new users, someone knowing roughly what to expect will find the detailed information here. The diagrams and tables are models of clarity and design - I can imagine the huge amount of effort and skill that must have gone into their creation. Too often documentation can take a back seat, but this manual is of the same high standard as the other components of the WP 34S project.
My heartfelt thanks to everyone involved. I haven't had so much fun with a calculator for a very long time, and there is still lots more to play with!
One small suggestion: the fraction separator is currently the same height as the digits 0-9. As such it doesn't (for me) clearly separate the numerator and denominator. Old Casio calculators used a separator made from the bottom and bottom-right segments: this half-height character provided a clear break in the string of digits. Would this be a possible change?
Nigel (UK)