As I wrote in previous post, I have to be constantly cleaning it. It gets lint on it very, very easily & then loses its traction. The instructions say to use baby wipes to clean the back of it, to cut it to the size of your machine bed if you don't have a drop-in cabinet & to tape it down really well. I have the extra-sticky masking tape. I didn't follow the instructions about cutting it to size because I've asked my family for help building a sewing table for Christmas. I have some chocolate boxes surrounding my machine to provide a larger surface to support my quilts for FMQ.
If you get muscle cramps/fatigue from FMQ, I'd say the Supreme Slider is worth the cost. If you're just looking for something to improve your stitch quality, I'd move this tool down the list. Switching to Aurifil thread actually made more of a difference in the quality of my stitches than the Supreme Slider did.