I still can't find anything that beats my HP 50g (either physical or running in one of the emulators) for just about any kind of computation involving several pieces of data. For more data, a spreadsheet is really hard to beat.
You’re not wrong on the syntax stuff, but as long as the math operations are there, it’ll do what you want. The special stuff for currency or other conversions isn’t very hard to get the hang of once you start using an app.
Really, the frustrating thing is when I’m on a machine that’s not mine and I hit my Soulver system-wide shortcut and can’t open up my scratchpad. But that’s my problem.
$425 * 3 in £
Once you've got "in £" you know it's available anywhere. I use it a lot for unit conversion too:
3 inches in mm
The other thing I use a lot is referencing other lines. So this will output £4:
£10 + 2
line1 / 3
For me, the go-to for multi-line calculations is Octave. At that point I can annotate to my hearts desire, plus I've always preferred Octave plotting over spreadsheet functions.
The ability to share your calculations nearly universally, though, is the major advantage of spreadsheets.
Eg "what % of 198 is 22" You can still calculate this the normal way, but this syntax sugar is natural enough and easier to remember.
Or the other big example somebody already posted is currency conversion. "1 USD to GBP"
Even if you don't use any of that, the ability to have a readable notebook, variables, and other features make it far better than a traditional calculator. I could never go back.
edit: when I'm "deep in it" this is similar to what I use Excel/GDocs for, but they're heavier than I'd like for more casual use. I spend half the time I'm using a spreadsheet in Google looking at documentation for Excel functions.