Relative line numbers are especially useful when you have mis- or not configured moving by paragraphs/defuns/classes/etc. for some particular mode. C-16 C-p will move the point 16 lines up, for example, supposedly exactly where you want it to be. But that's not the use case I need line numbers for - actually, well configured movement commands + isearch + ace-jump + iy-goto-char + occur is a combo which makes relative line numbering completely unnecessary.
I use (non-relative) line numbers quite often though, and it when I need to tell my colleague that there is this function in some file, on line 323, with a some interesting statement between lines 330 and 336. This makes it extremely easy for them to get to where I am and see exactly what I see; and on the other hand I don't need to move point to those three lines to read their numbers or - absolutely nightmarish - to count the positions manually - they are just there, for me to see.
It would be better to show and hide linum with some simple binding, but I'm already used to them, so it's not a big deal for me.
I use (non-relative) line numbers quite often though, and it when I need to tell my colleague that there is this function in some file, on line 323, with a some interesting statement between lines 330 and 336. This makes it extremely easy for them to get to where I am and see exactly what I see; and on the other hand I don't need to move point to those three lines to read their numbers or - absolutely nightmarish - to count the positions manually - they are just there, for me to see.
It would be better to show and hide linum with some simple binding, but I'm already used to them, so it's not a big deal for me.