The HP35S is a welcome return to form for HP, but ...
1. There's no communications in the HP35S unlike the 48/49/50 series, so the only way to load programs is to key them in by hand
2. The keyboard quality while OK, is nothing like as good as my old 48G or even my 1990s 32Sii. My 35S had a sticky right arrow key. Mercifully the after sales service is still good and the whole calculator was replaced within a week. The problem is not so much the absence or presence of a positive click, but rather the design and layout: I know it's a matter of taste but I dislike the arrow keys; I would prefer more space between some of the keys; and I thought the old 32Sii layout was more logical.
3. The two line display is nice, and makes RPN rather easier to understand as you can see the top two numbers in the stack instead of just the top one, but it would have been even nicer to have four lines and to be able to see the whole stack. The most irritating feature is that long numbers scroll off to the right.
4. The hex mode is very odd. In hex mode if you enter a normal number say "12" it's treated as a decimal and converted to hex ("Ch"). If you want to enter a hex value you have to add a trailing "h" by keying "blue shift, 1, 6" which is not exactly intuitive. Even more strangely you enter "ABCDEF" by using the keys labelled "HIJKLM".
5. The complex number support is welcome but oddly incomplete. For example the square root button doesn't work. If you enter "-1 SQRT" you get an error instead of "0i1", even if you enter "-1i0 SQRT" you still get an error, even though "-1i0 .5 y^x" does give you the right answer!
Overall I like it, especially the nice case it comes in, but if you want a more usable simple scientific calculator try to get hold of an old HP32Sii or 42S, and if you want a better less brain-dead design then save up for a HP50G or an old 48GX.