I've used them. Took a class on a Celtic Heart wallhanging - it was all bias. The strips came out a little larger than 1/4"
We cut 1"?(can't remember) bias strips, folded them, and sewed with a 1/4" seam. Then trimmed the seam and ironed the bias flat from the top with the trimmed seam underneath. We used the bias bars to press seam underneath as it doesn't show. Then you use a glue stick to hold bias strips on pattern, and can stitch with decorative, straight or zigzag to keep them down.
I liked the method so well I used it on a stained glass wallhanging rather than the bias tape they sell. A little larger, maybe, but it worked just as well.