Customer Rating: 
Summary: Good price but overall a letdown
Comment: There are some really thorough reviews written already but I'll add my $0.02 just to give some added perspective for the potential buyer.
I'm an electronics engineer and got my original HP-41C while in college--been using it off and on for about 25 years until it died last week. I have been looking for an RPN calculator to replace it. I read the reviews for the HP-35s and got the impression it was a worthy successor to that well-made HP-41.
It arrived yesterday so I've just had a few hours with it so here goes.
1) It comes with a Quick Start Guide of only a few pages with the real 382 page manual on CD. Bad impression #1: I have to print a 382 page manual just to learn how it works!
2) Some of the reviews stated that the button tactile feel was just like the -41 and -11C era. I disagree. It does have a tactile click but not the satisfying feel of my -41. Bad impression #2: weak tactile button feel.
3) It is clear that HP dropped the ball on the best engineering calculators on the market, maybe from the split from Agilent and more cost pressure on the consumer-oriented HP side. The display quality is weak. The two line display in RPN mode does show the X and Y stack registers but the rectangular (not square) pixels in the matrix display make for jagged numbers--like the early days of LCDs. It's remarkable to me that in 25 years they weren't able to add any significant improvements to the display quality or features. How about a backlight or OLED display? To be fair it is a heck of a lot cheaper than my -41 cost but there has been a lot of technology improvement in the generation that has passed. Bad impression #3: weak display.
4) I do a lot of binary and hex conversions and they really didn't try to get that right. Too many button presses required for simple conversions, and hex digits A-F aren't even marked on the keyboard--you just have to remember that the 1/x key is hex "F".
5) It's got some nice unit conversions and handles complex numbers but not any more than a Casio or TI calculator has. It does have a good equation solver and numerical integration solver it appears. But in programming, only a single letter for program name? What's up with that?
In summary, I like RPN and it was about the only choice out there for scientific use. It is still a usable calculator but it is a sad testament to how a product line can deteriorate from excellence to, well, mediocrity. It does seem to reflect the mediocre engineering and lack of innovation of the HP laptops which I would not own. But hey, at least I've got a RPN calculator again.
Customer Rating: Summary: Back to HP and RPN
Comment: My first HP calculator was purchased in 1986 when I was an undergrad in engineering (HP 15C)- RPN took a little to get used to, but it was worth the effort. For grad school I upgraded to an HP 28S, which was state of the art back then. Over the past ten years or so, I have reverted back to using an algebraic calculator at work.
Recently, a new coworker showed me his HP 33S. The price was right and it could be used in either algebraic or RPN modes. I wanted to get back to RPN and read the on line reviews for both the 33S and 35S calculators. For how I use a calculator at work, the 35S price and convenience of having an RPN calculator again was right for me.
I'm back to using an HP, on RPN mode, and happy that I made the move!
Customer Rating: Summary: The best HP RPN Calc in 20 years!
Comment: My personal opinion is the 42s was the pinnacle of pocket sized excellence. The larger models afterwards are too big physically to be handy. I use: 42s, 35s, 48sx, 33s, Ti-89 (in order of preference). Primary use is electronic design, base conversions, using many self-coded macros/functions/programs in the calculator.
The 35s offers a "HP 42s Lite" in a way. In all, I miss the label/menu interface used on the 42s. I'll buy another 35s just in case, though, since HP seems to be drifting away from making Good Calculators, and compromising to the the "= user". The 35s is the first sign I've seen in 10 years that HP realizes the market for a True Programmable RPN Calc.
Things to note about the 35s, vis a vis 42s and other "classic" HP designs:
Only Single letter/number storage/program labels. HP Had Word size labels in 1990 on the 42s, this calculator is the same physical size, with more inputs (left and right shift, the 42s only had one shift). With the advances in semiconductors, I am shocked to see this (mild) limitation. In actual use, I haven't used over 30 program names, but it is very nice to give them a meaningful 'name' instead of a letter/number label.
Others' comments detail some minor usage issues, many are due to incorrect mode chosen (RPN/ALG), some are actual annoyances (hex/binary entry).
The 35s gives me most all of the functionality of the 42s, many extra features over the 42s, and I don't need to spend $400+ to get it at an auction.
Bulletproof Construction. Calculator is solid, keys have the snappy tactile feel famous of HP. I have no doubt this too, like my 42s, will last for Decades of use.
The 35s Comes with the best hard/zippered case I've seen on "consumer calculators".
If you are a student, keep this in mind: In everyday/Real World work since college, I've used the SAME 42s in my daily environment (17 years). I haven't really touched the graphing 48sx. This is a large "feature" one needs to pay attention to, and the reason so many people "collect" HP Calculators, as well as use them. Once you are used to one calculator and functions, switching to another slows you down A LOT. I haven't run into a situation where an "Algebraic" Calculator can do something faster or simpler than an RPN calculator, both in keystrokes, and processing time.
If you are used to RPN, you will not regret this purchase! (unlike the 33s...)
If you are used to an = sign, but want to learn RPN, then this is the perfect choice for transition!
I am hoping for the release of a 42sII, but I'll happily survive with the 35s until then.
