It seems to me like the second example's readability stems almost entirely from the indent increase. I don't see how the stacking helps or doesn't help at all. I just saw the addition linebreaks as noise that ruins the flow of the code.
Even with the current example, I immediately said, "Inside the let." The only uncertainty for a half-second in my head was with the with-open, but that's only because 2-space tabs are pretty tight and long functions like that make reading the drop harder.
Indeed. And if your eyes aren't up to detecting that (this function is indeed long), EMACS has traditionally had two ways of manually finding that out: previous line retains the current column number, so you can position yourself at the println's opening paren and then go up. Or automatic highlighting (blinking in the monochrome days) when the point is over the closing paren.
In my personal experience (e.g. reading Lisp Machine system code) it hasn't often been a major problem. Then again I think I'm really good at following aligned columns and I can see other people not being good at this.
Even with the current example, I immediately said, "Inside the let." The only uncertainty for a half-second in my head was with the with-open, but that's only because 2-space tabs are pretty tight and long functions like that make reading the drop harder.