No. i have never owned straps. i can't figure them out to be honest.
It would be worth it even for back work like heavy pulldowns or chins. Sometimes you need to just get your grip out of an exercise. Your grip can limit you by deciding how much you will pull and how long you will hang on to the load.
If you buy em and can't figure em' out, I will personally make you an instructional video.
Here's one, but it ain't me babe... no no no it ain't me (sorry was thinkin about Bob Dylan)