I, too, have the Rubicoil that I bought from Bonnie's Best and it's wonderful!!
I had a different, less expensive ($45) coil binder before (NOT a Carl Craft, so I can't speak about that one), but it had plastic parts. I had only been putting two sheets of 20lb. sheets of copy paper in it, but that was taking too long to punch all the sheets. I decided to try to speed it up by using three sheets and a plastic part inside broke ... right in the middle of a cookbook project. The Rubicoil is all metal parts and so easy to use!! "It will punch six to eight pages of light-weight paper at a time and it will also punch three to four sheets of cardstock, as well as two sheets of lightweight cardboard at a time for book covers!" I am so glad I bought it. It was worth every penny to me.
I also agree with angiecrop about Bonniesbest.com service.
http://www.bonniesbest.com/spiralcoilbinding.htm
Got it quickly and she is a pleasure to do business with!!