The tensioner allows me to tune the blade like a guitar string, but in steps if I want to fold the tensioner handle out of the way.
With a Starret 18 tpi bi-metal blade tuned up to about middle C, I got through a 1.5" round piece of 60-61 Aluminum in 1 minute 15 seconds with ~100 strokes.
I got the new hack saw as an alternative to buying a metal cutting band saw, as it is cheaper, more portable, and takes up less shop space. It is not nearly as fast, easy, and accurate as my brother's Jet band saw, but I don't cut thick metal but once a month.