My shop heavily pushes this foot. It isn't really free motion, but you can do a lot of curves and such (doing straight line shapes like triangles would be really tough). It's a good one for applique round shapes, and it does a nice job of echo quilting. We use it ALL the time in classes. It does give even stitches because it is feed-dogs up, not true free motion.
For me- I've never wanted to buy it. It is a very expensive foot, and kind of more a novelty. You can do a lot more with a darning foot and just do actual free motion quilting. If you want even stitches, practice.
Here's a video for those wanting to see it in action-
https://www.youtube.com/watch?v=JfHV...DE59CCCEE8C513