I've had a couple. They require a lot of skill to use correctly. Most people find them pretty frustrating.

Instead of investing in a binding foot, I would recommend trying a form of "invisible" machine binding. It is demonstrated in this Youtube video:
http://www.youtube.com/watch?v=wprg5vzkuGw

I have a Pfaff bi-level foot which is amazing. It's still a 2 step process though. but the finish is much better than I could do with an ordinary foot. I love this foot and I've not bound anything by hand since I got this foot.

http://www.pfaffusa.com/5436_8394.html

Nope don't have one, and don't want one.

I also have found this foot to be very effective. For all Pfaff owners reading: do yourselves a favor and consider adding this foot to your arsenal.

I bought a cheap one years ago for sewing pre-packaged bias binding on things such as potholders, etc. It was supposed to sew all layers at one time, but I found it impossible to do a neat job ... stuff was slipping and sliding every which way; I assume doing a one-step quilt binding would be a real "Mission Impossible". I saw a professional quilter on t.v. several years ago who had a large, sophisticated and expensive piece of equipment for that, but it was not an item for the average home quilter.

How do you use it to attach binding?

If you go to the link that gailmitchell posted to the Pfaff site, there is a link to a short video showing it in use.

I have one. I have only used it on satin binding, which is a pain in the neck anyways. I would not use the foot for satin binding again. I will be finishing another quilt soon, I'll let you know what I think of it with cotton binding.
Thanks!

Last week I watched the Baby Lock serger lady (demonstrator) use the double fold binder on the Evolution serger and I was instantly sold on it.
karen