I took the time to properly learn and use emacs-calc this year, after being an emacs user anyway. Before that, I tended to use bc on the shell for quick calculations, but always felt that to be too limited.

Since then I am practically a daily user.

It's not without downsides, and some simple workflows that seem common and trivial to me personally feel a bit awkward and contorting. For example, working with variables/equations, with that '=>' "operator", is rather strange. There also seems to be no support for hex numbers in 0x-prefixed lowercase notation, which makes it hard to impossible to just copy and paste hex numbers for programming. And while emacs-calc has a very impressive scientific unit system, often I just want to use unit prefixes, like u,m,M for micro,milli,Mega respectively, without having to resort to using actual physical units in my calculations (and then finding out again how to simplify appropriately).

I also almost don't use the trail at all, mostly because its navigation and actioning feels tedious and downright archaic, making me think that emacs-calc probably started out a few decades ago, with a specific, now outdated, terminal paradigm in mind.

But all in all, it's pretty impressive, and fills the role as my daily companion for quick, and sometimes more elaborate, computations well.