[badsectoracula]

Well, technically the API is still available pretty much everywhere (be it directly or via a wrapper library) and most hardware still has support for drawing lines, so it is still easy in current days to do things like this too :-P.

I'm using it all the time when i want to draw lines in 3D.

(though as far as lines and OpenGL is concerned i remember reading ages ago that not even SGI's implementation had full support for everything OpenGL was supposedly able to do)

[pixelesque]

The API still exists, but in most implementations things like line styles and thickness are no longer supported.

[badsectoracula]

Not sure about line styles but so far i haven't seen any implementation that doesn't support line thickness (though i only use OpenGL on desktop).