next makes it harder (or impossible) to prove your program correct, and Djikstra was all about proof of correctness.

I personally think the way next is employed can make a huge difference in readability and understandability. I would rather be able to say next if this; next if that; next if the_other; and then the rest of the loop; I find that much easier to understand.

I don't care much whether I can prove it if I can read it.