Interesting. A similar feature built into Vim is `cursorcolumn`, which will highlight the background of whatever column the cursor is in. If you set `cursorline` as well, you get a kind of cross-hairs around the cursor. See e.g. http://briancarper.net/vim/cursorcol.png

I find that feature useful enough that I've never needed indent guides. If you jump the cursor to the beginning of a line, you can easily see which other lines are indented equally with that line.