The feedback lets you know what the position is. Without it you need some other way to figure that out, and this can be anything, including switches or your own potentiometer. Or you can just run it from stop to stop and let the limit switches stop it.
I bought a linear actuator (with feedback) and JRK controller a couple years ago and the pair have been operating perfectly, outside, every day, in temperatures from -15F to 100F. I initially thought it was too much money and overkill. I am really happy with the results. Totally worth it, especially for all the JRK features and settings.