First Impressions

[Tugdual]

I also have kinda mixed feelings with this Hp Prime. I share your concerns regarding the quality of the screen and more specifically the angle. You can't read it unless you actually bend over the table; this being said, the touch screen will require that you bend over the table anyway. Also you seem to be happy with the touch screen but bear in mind it is supposed to manage two fingers and so far I lack the zoom with two fingers on most applications (though using +/- keys is acceptable but disappointing).
Even the bigger font is too small and difficult to read compared with old school HP 15C (not even talking about lack of big numbers formatting with separators every 3 digits which was definitely a plus on the former models).
Still on the hardware side, like many other users I find the keyboard very good and I'm happy with the case format and light weight. I don't like the keyboard colors; orange and blue cannot be read on white keys! Orange and blue are typical HP color codes but this worked well on dark keys which was the case on the 15C for example. Unfortunately that cannot be changed any longer now (unless we could have replacement kits with dark keys?).
What I expect from a pocket calculator is to make the best possible usage of keys otherwise I use a computer. Initially I found it slower to use the Prime so I decided to compare a bit more formally the number of required keystrokes for various operations in between 15C and Prime and found that I had a wrong perception: the Prime is quite efficient thanks to the graphical view (compare Matrices in between 15C and Prime, it is quite obvious the prime is much faster). This being said I don't like the scolling menus and the abuse of ALPHA keys for everything; again the Prime is a calculator, not a computer and typing instructions is not efficient. Considering the number of functions, I understand we shall need a flexible input systems and using the touch screen is quite a good idea but then I would really prefer to see large buttons on screen with a reduced area to display the ongoing calculations (after all the 15C had only 1 line and true RPN users don't need to see the stack...).
There are many other weaknesses. Like conversions of measurement units or integer format (hex, dec, bin) are super un-efficient and sometime just refuse to work (I struggled with C° to F° conversions and did it manually, much faster!). I was expecting to use that for my work an this is just ridiculous how difficult it is. I may have to do a specific program just for this. Sometime the calculator tells me I cannot do a calculation and I have no idea why. There is little diagnostic ande feedback returned by the firmware and you often feel silly wondering if this is a bug or something you didn't catch. Even if this is something I didn't catch, this shouldn't be a blocker. Also there are many limitations depending if you use RPN, comma or dot for decimal places, may be more and sometime using the calculator is like exploring the jungle.
Still talking about firmware, I regret that there is no easy way to transfer CAS to applications without going for painful substitutions just because for some obscure reasons, CAS uses lower case while the whole rest uses upper case. If I had to chose, I would definitely have everything lower case BTW... First thing I tried was to draw a function and its derivate and that took me quite some time to understand how to do that!

Finally, because of: the lack of efficiency, the confusing internal conflicts totally stoping you and sometime bugs, I kept the calculator for me while it was my intention to give it to my daughter for her studies but I felt like sabotaging her work.

This being said, considering that most of the issues I mentioned are related to the firmware while the hardware is pretty good, I feel like the prime has a very high potential and I would really appreciate if Hp could either improve the firmware or have it open source and let the community somehow help. And also don't take all my comments negatively, the Prime has some very good aspects and if I share my opinion it is really because I expect to see it improving.