The trade-off was supposed to be that the heavy power train didn't need to be carried aloft as in horizontal axis turbines, but seeing proper angle of attack only a small portion of a rotation was too much to overcome.

On the plus side, such turbines are easy to build, transport (by donkey even) and erect, so may prove to be useful in windy 3rd world applications.

Here's one in the Tehachapis that mirrors those in the Altamont Pass.

"Life shrinks or expands in proportion to one's courage." - Anaïs Nin