I can't comment on the ruler, but I have Beba's lazy susan rotating cutting mats. I got the small (10X10) at a show and the largest one on ebay. The thing that I really like is that they have a piece of felt on the bottom so the mat turns easily, but when you put pressure on to make the cut the felt compresses just the right amount so the feet on the unit contact your table which keeps the mat stable allowing you to cut without a wiggle. They are very heavy.
http://www.bebasboutique.com/product-demos-1.html