It is a great, cheap solution. Just beware that the rpms won’t stay there when you start getting load. What you’re adjusting is the power going in, not the rpms coming out, so when more of the power goes into the material, the rpms will get lower.
I use it (used to, the 611 has basically the same thing in the router) just to tune it by ear when I’m cutting. I might turn it up or down a little if things sound funny or there’s chatter. It’s definitely a good cheap speed controller.